src/librustc/hir/print.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 pub use self::AnnNode::*;
  12
  13 use syntax::abi::Abi;
  14 use syntax::ast;
  15 use syntax::codemap::{CodeMap, Spanned};
  16 use syntax::parse::ParseSess;
  17 use syntax::parse::lexer::comments;
  18 use syntax::print::pp::{self, Breaks};
  19 use syntax::print::pp::Breaks::{Consistent, Inconsistent};
  20 use syntax::print::pprust::PrintState;
  21 use syntax::ptr::P;
  22 use syntax::symbol::keywords;
  23 use syntax::util::parser::{self, AssocOp, Fixity};
  24 use syntax_pos::{self, BytePos};
  25
  26 use hir;
  27 use hir::{PatKind, RegionTyParamBound, TraitTyParamBound, TraitBoundModifier, RangeEnd};
  28
  29 use std::cell::Cell;
  30 use std::io::{self, Write, Read};
  31 use std::iter::Peekable;
  32 use std::vec;
  33
  34 pub enum AnnNode<'a> {
  35     NodeName(&'a ast::Name),
  36     NodeBlock(&'a hir::Block),
  37     NodeItem(&'a hir::Item),
  38     NodeSubItem(ast::NodeId),
  39     NodeExpr(&'a hir::Expr),
  40     NodePat(&'a hir::Pat),
  41 }
  42
  43 pub enum Nested {
  44     Item(hir::ItemId),
  45     TraitItem(hir::TraitItemId),
  46     ImplItem(hir::ImplItemId),
  47     Body(hir::BodyId),
  48     BodyArgPat(hir::BodyId, usize)
  49 }
  50
  51 pub trait PpAnn {
  52     fn nested(&self, _state: &mut State, _nested: Nested) -> io::Result<()> {
  53         Ok(())
  54     }
  55     fn pre(&self, _state: &mut State, _node: AnnNode) -> io::Result<()> {
  56         Ok(())
  57     }
  58     fn post(&self, _state: &mut State, _node: AnnNode) -> io::Result<()> {
  59         Ok(())
  60     }
  61 }
  62
  63 pub struct NoAnn;
  64 impl PpAnn for NoAnn {}
  65 pub const NO_ANN: &'static PpAnn = &NoAnn;
  66
  67 impl PpAnn for hir::Crate {
  68     fn nested(&self, state: &mut State, nested: Nested) -> io::Result<()> {
  69         match nested {
  70             Nested::Item(id) => state.print_item(self.item(id.id)),
  71             Nested::TraitItem(id) => state.print_trait_item(self.trait_item(id)),
  72             Nested::ImplItem(id) => state.print_impl_item(self.impl_item(id)),
  73             Nested::Body(id) => state.print_expr(&self.body(id).value),
  74             Nested::BodyArgPat(id, i) => state.print_pat(&self.body(id).arguments[i].pat)
  75         }
  76     }
  77 }
  78
  79 pub struct State<'a> {
  80     pub s: pp::Printer<'a>,
  81     cm: Option<&'a CodeMap>,
  82     comments: Option<Vec<comments::Comment>>,
  83     literals: Peekable<vec::IntoIter<comments::Literal>>,
  84     cur_cmnt: usize,
  85     boxes: Vec<pp::Breaks>,
  86     ann: &'a (PpAnn + 'a),
  87 }
  88
  89 impl<'a> PrintState<'a> for State<'a> {
  90     fn writer(&mut self) -> &mut pp::Printer<'a> {
  91         &mut self.s
  92     }
  93
  94     fn boxes(&mut self) -> &mut Vec<pp::Breaks> {
  95         &mut self.boxes
  96     }
  97
  98     fn comments(&mut self) -> &mut Option<Vec<comments::Comment>> {
  99         &mut self.comments
 100     }
 101
 102     fn cur_cmnt(&mut self) -> &mut usize {
 103         &mut self.cur_cmnt
 104     }
 105
 106     fn cur_lit(&mut self) -> Option<&comments::Literal> {
 107         self.literals.peek()
 108     }
 109
 110     fn bump_lit(&mut self) -> Option<comments::Literal> {
 111         self.literals.next()
 112     }
 113 }
 114
 115 #[allow(non_upper_case_globals)]
 116 pub const indent_unit: usize = 4;
 117
 118 #[allow(non_upper_case_globals)]
 119 pub const default_columns: usize = 78;
 120
 121
 122 /// Requires you to pass an input filename and reader so that
 123 /// it can scan the input text for comments and literals to
 124 /// copy forward.
 125 pub fn print_crate<'a>(cm: &'a CodeMap,
 126                        sess: &ParseSess,
 127                        krate: &hir::Crate,
 128                        filename: String,
 129                        input: &mut Read,
 130                        out: Box<Write + 'a>,
 131                        ann: &'a PpAnn,
 132                        is_expanded: bool)
 133                        -> io::Result<()> {
 134     let mut s = State::new_from_input(cm, sess, filename, input, out, ann, is_expanded);
 135
 136     // When printing the AST, we sometimes need to inject `#[no_std]` here.
 137     // Since you can't compile the HIR, it's not necessary.
 138
 139     s.print_mod(&krate.module, &krate.attrs)?;
 140     s.print_remaining_comments()?;
 141     s.s.eof()
 142 }
 143
 144 impl<'a> State<'a> {
 145     pub fn new_from_input(cm: &'a CodeMap,
 146                           sess: &ParseSess,
 147                           filename: String,
 148                           input: &mut Read,
 149                           out: Box<Write + 'a>,
 150                           ann: &'a PpAnn,
 151                           is_expanded: bool)
 152                           -> State<'a> {
 153         let (cmnts, lits) = comments::gather_comments_and_literals(sess, filename, input);
 154
 155         State::new(cm,
 156                    out,
 157                    ann,
 158                    Some(cmnts),
 159                    // If the code is post expansion, don't use the table of
 160                    // literals, since it doesn't correspond with the literals
 161                    // in the AST anymore.
 162                    if is_expanded {
 163                        None
 164                    } else {
 165                        Some(lits)
 166                    })
 167     }
 168
 169     pub fn new(cm: &'a CodeMap,
 170                out: Box<Write + 'a>,
 171                ann: &'a PpAnn,
 172                comments: Option<Vec<comments::Comment>>,
 173                literals: Option<Vec<comments::Literal>>)
 174                -> State<'a> {
 175         State {
 176             s: pp::mk_printer(out, default_columns),
 177             cm: Some(cm),
 178             comments: comments.clone(),
 179             literals: literals.unwrap_or_default().into_iter().peekable(),
 180             cur_cmnt: 0,
 181             boxes: Vec::new(),
 182             ann,
 183         }
 184     }
 185 }
 186
 187 pub fn to_string<F>(ann: &PpAnn, f: F) -> String
 188     where F: FnOnce(&mut State) -> io::Result<()>
 189 {
 190     let mut wr = Vec::new();
 191     {
 192         let mut printer = State {
 193             s: pp::mk_printer(Box::new(&mut wr), default_columns),
 194             cm: None,
 195             comments: None,
 196             literals: vec![].into_iter().peekable(),
 197             cur_cmnt: 0,
 198             boxes: Vec::new(),
 199             ann,
 200         };
 201         f(&mut printer).unwrap();
 202         printer.s.eof().unwrap();
 203     }
 204     String::from_utf8(wr).unwrap()
 205 }
 206
 207 pub fn visibility_qualified(vis: &hir::Visibility, w: &str) -> String {
 208     to_string(NO_ANN, |s| {
 209         s.print_visibility(vis)?;
 210         s.s.word(w)
 211     })
 212 }
 213
 214 impl<'a> State<'a> {
 215     pub fn cbox(&mut self, u: usize) -> io::Result<()> {
 216         self.boxes.push(pp::Breaks::Consistent);
 217         self.s.cbox(u)
 218     }
 219
 220     pub fn nbsp(&mut self) -> io::Result<()> {
 221         self.s.word(" ")
 222     }
 223
 224     pub fn word_nbsp(&mut self, w: &str) -> io::Result<()> {
 225         self.s.word(w)?;
 226         self.nbsp()
 227     }
 228
 229     pub fn head(&mut self, w: &str) -> io::Result<()> {
 230         // outer-box is consistent
 231         self.cbox(indent_unit)?;
 232         // head-box is inconsistent
 233         self.ibox(w.len() + 1)?;
 234         // keyword that starts the head
 235         if !w.is_empty() {
 236             self.word_nbsp(w)?;
 237         }
 238         Ok(())
 239     }
 240
 241     pub fn bopen(&mut self) -> io::Result<()> {
 242         self.s.word("{")?;
 243         self.end() // close the head-box
 244     }
 245
 246     pub fn bclose_(&mut self, span: syntax_pos::Span, indented: usize) -> io::Result<()> {
 247         self.bclose_maybe_open(span, indented, true)
 248     }
 249     pub fn bclose_maybe_open(&mut self,
 250                              span: syntax_pos::Span,
 251                              indented: usize,
 252                              close_box: bool)
 253                              -> io::Result<()> {
 254         self.maybe_print_comment(span.hi())?;
 255         self.break_offset_if_not_bol(1, -(indented as isize))?;
 256         self.s.word("}")?;
 257         if close_box {
 258             self.end()?; // close the outer-box
 259         }
 260         Ok(())
 261     }
 262     pub fn bclose(&mut self, span: syntax_pos::Span) -> io::Result<()> {
 263         self.bclose_(span, indent_unit)
 264     }
 265
 266     pub fn in_cbox(&self) -> bool {
 267         match self.boxes.last() {
 268             Some(&last_box) => last_box == pp::Breaks::Consistent,
 269             None => false,
 270         }
 271     }
 272     pub fn space_if_not_bol(&mut self) -> io::Result<()> {
 273         if !self.is_bol() {
 274             self.s.space()?;
 275         }
 276         Ok(())
 277     }
 278     pub fn break_offset_if_not_bol(&mut self, n: usize, off: isize) -> io::Result<()> {
 279         if !self.is_bol() {
 280             self.s.break_offset(n, off)
 281         } else {
 282             if off != 0 && self.s.last_token().is_hardbreak_tok() {
 283                 // We do something pretty sketchy here: tuck the nonzero
 284                 // offset-adjustment we were going to deposit along with the
 285                 // break into the previous hardbreak.
 286                 self.s.replace_last_token(pp::Printer::hardbreak_tok_offset(off));
 287             }
 288             Ok(())
 289         }
 290     }
 291
 292     // Synthesizes a comment that was not textually present in the original source
 293     // file.
 294     pub fn synth_comment(&mut self, text: String) -> io::Result<()> {
 295         self.s.word("/*")?;
 296         self.s.space()?;
 297         self.s.word(&text[..])?;
 298         self.s.space()?;
 299         self.s.word("*/")
 300     }
 301
 302
 303     pub fn commasep_cmnt<T, F, G>(&mut self,
 304                                   b: Breaks,
 305                                   elts: &[T],
 306                                   mut op: F,
 307                                   mut get_span: G)
 308                                   -> io::Result<()>
 309         where F: FnMut(&mut State, &T) -> io::Result<()>,
 310               G: FnMut(&T) -> syntax_pos::Span
 311     {
 312         self.rbox(0, b)?;
 313         let len = elts.len();
 314         let mut i = 0;
 315         for elt in elts {
 316             self.maybe_print_comment(get_span(elt).hi())?;
 317             op(self, elt)?;
 318             i += 1;
 319             if i < len {
 320                 self.s.word(",")?;
 321                 self.maybe_print_trailing_comment(get_span(elt), Some(get_span(&elts[i]).hi()))?;
 322                 self.space_if_not_bol()?;
 323             }
 324         }
 325         self.end()
 326     }
 327
 328     pub fn commasep_exprs(&mut self, b: Breaks, exprs: &[hir::Expr]) -> io::Result<()> {
 329         self.commasep_cmnt(b, exprs, |s, e| s.print_expr(&e), |e| e.span)
 330     }
 331
 332     pub fn print_mod(&mut self, _mod: &hir::Mod, attrs: &[ast::Attribute]) -> io::Result<()> {
 333         self.print_inner_attributes(attrs)?;
 334         for &item_id in &_mod.item_ids {
 335             self.ann.nested(self, Nested::Item(item_id))?;
 336         }
 337         Ok(())
 338     }
 339
 340     pub fn print_foreign_mod(&mut self,
 341                              nmod: &hir::ForeignMod,
 342                              attrs: &[ast::Attribute])
 343                              -> io::Result<()> {
 344         self.print_inner_attributes(attrs)?;
 345         for item in &nmod.items {
 346             self.print_foreign_item(item)?;
 347         }
 348         Ok(())
 349     }
 350
 351     pub fn print_opt_lifetime(&mut self, lifetime: &hir::Lifetime) -> io::Result<()> {
 352         if !lifetime.is_elided() {
 353             self.print_lifetime(lifetime)?;
 354             self.nbsp()?;
 355         }
 356         Ok(())
 357     }
 358
 359     pub fn print_type(&mut self, ty: &hir::Ty) -> io::Result<()> {
 360         self.maybe_print_comment(ty.span.lo())?;
 361         self.ibox(0)?;
 362         match ty.node {
 363             hir::TySlice(ref ty) => {
 364                 self.s.word("[")?;
 365                 self.print_type(&ty)?;
 366                 self.s.word("]")?;
 367             }
 368             hir::TyPtr(ref mt) => {
 369                 self.s.word("*")?;
 370                 match mt.mutbl {
 371                     hir::MutMutable => self.word_nbsp("mut")?,
 372                     hir::MutImmutable => self.word_nbsp("const")?,
 373                 }
 374                 self.print_type(&mt.ty)?;
 375             }
 376             hir::TyRptr(ref lifetime, ref mt) => {
 377                 self.s.word("&")?;
 378                 self.print_opt_lifetime(lifetime)?;
 379                 self.print_mt(mt)?;
 380             }
 381             hir::TyNever => {
 382                 self.s.word("!")?;
 383             },
 384             hir::TyTup(ref elts) => {
 385                 self.popen()?;
 386                 self.commasep(Inconsistent, &elts[..], |s, ty| s.print_type(&ty))?;
 387                 if elts.len() == 1 {
 388                     self.s.word(",")?;
 389                 }
 390                 self.pclose()?;
 391             }
 392             hir::TyBareFn(ref f) => {
 393                 let generics = hir::Generics {
 394                     lifetimes: f.lifetimes.clone(),
 395                     ty_params: hir::HirVec::new(),
 396                     where_clause: hir::WhereClause {
 397                         id: ast::DUMMY_NODE_ID,
 398                         predicates: hir::HirVec::new(),
 399                     },
 400                     span: syntax_pos::DUMMY_SP,
 401                 };
 402                 self.print_ty_fn(f.abi, f.unsafety, &f.decl, None, &generics,
 403                                  &f.arg_names[..])?;
 404             }
 405             hir::TyPath(ref qpath) => {
 406                 self.print_qpath(qpath, false)?
 407             }
 408             hir::TyTraitObject(ref bounds, ref lifetime) => {
 409                 let mut first = true;
 410                 for bound in bounds {
 411                     self.nbsp()?;
 412                     if first {
 413                         first = false;
 414                     } else {
 415                         self.word_space("+")?;
 416                     }
 417                     self.print_poly_trait_ref(bound)?;
 418                 }
 419                 if !lifetime.is_elided() {
 420                     self.word_space("+")?;
 421                     self.print_lifetime(lifetime)?;
 422                 }
 423             }
 424             hir::TyImplTraitExistential(ref bounds) |
 425                 hir::TyImplTraitUniversal(_, ref bounds) => {
 426                 self.print_bounds("impl", &bounds[..])?;
 427             }
 428             hir::TyArray(ref ty, v) => {
 429                 self.s.word("[")?;
 430                 self.print_type(&ty)?;
 431                 self.s.word("; ")?;
 432                 self.ann.nested(self, Nested::Body(v))?;
 433                 self.s.word("]")?;
 434             }
 435             hir::TyTypeof(e) => {
 436                 self.s.word("typeof(")?;
 437                 self.ann.nested(self, Nested::Body(e))?;
 438                 self.s.word(")")?;
 439             }
 440             hir::TyInfer => {
 441                 self.s.word("_")?;
 442             }
 443             hir::TyErr => {
 444                 self.s.word("?")?;
 445             }
 446         }
 447         self.end()
 448     }
 449
 450     pub fn print_foreign_item(&mut self, item: &hir::ForeignItem) -> io::Result<()> {
 451         self.hardbreak_if_not_bol()?;
 452         self.maybe_print_comment(item.span.lo())?;
 453         self.print_outer_attributes(&item.attrs)?;
 454         match item.node {
 455             hir::ForeignItemFn(ref decl, ref arg_names, ref generics) => {
 456                 self.head("")?;
 457                 self.print_fn(decl,
 458                               hir::Unsafety::Normal,
 459                               hir::Constness::NotConst,
 460                               Abi::Rust,
 461                               Some(item.name),
 462                               generics,
 463                               &item.vis,
 464                               arg_names,
 465                               None)?;
 466                 self.end()?; // end head-ibox
 467                 self.s.word(";")?;
 468                 self.end() // end the outer fn box
 469             }
 470             hir::ForeignItemStatic(ref t, m) => {
 471                 self.head(&visibility_qualified(&item.vis, "static"))?;
 472                 if m {
 473                     self.word_space("mut")?;
 474                 }
 475                 self.print_name(item.name)?;
 476                 self.word_space(":")?;
 477                 self.print_type(&t)?;
 478                 self.s.word(";")?;
 479                 self.end()?; // end the head-ibox
 480                 self.end() // end the outer cbox
 481             }
 482             hir::ForeignItemType => {
 483                 self.head(&visibility_qualified(&item.vis, "type"))?;
 484                 self.print_name(item.name)?;
 485                 self.s.word(";")?;
 486                 self.end()?; // end the head-ibox
 487                 self.end() // end the outer cbox
 488             }
 489         }
 490     }
 491
 492     fn print_associated_const(&mut self,
 493                               name: ast::Name,
 494                               ty: &hir::Ty,
 495                               default: Option<hir::BodyId>,
 496                               vis: &hir::Visibility)
 497                               -> io::Result<()> {
 498         self.s.word(&visibility_qualified(vis, ""))?;
 499         self.word_space("const")?;
 500         self.print_name(name)?;
 501         self.word_space(":")?;
 502         self.print_type(ty)?;
 503         if let Some(expr) = default {
 504             self.s.space()?;
 505             self.word_space("=")?;
 506             self.ann.nested(self, Nested::Body(expr))?;
 507         }
 508         self.s.word(";")
 509     }
 510
 511     fn print_associated_type(&mut self,
 512                              name: ast::Name,
 513                              bounds: Option<&hir::TyParamBounds>,
 514                              ty: Option<&hir::Ty>)
 515                              -> io::Result<()> {
 516         self.word_space("type")?;
 517         self.print_name(name)?;
 518         if let Some(bounds) = bounds {
 519             self.print_bounds(":", bounds)?;
 520         }
 521         if let Some(ty) = ty {
 522             self.s.space()?;
 523             self.word_space("=")?;
 524             self.print_type(ty)?;
 525         }
 526         self.s.word(";")
 527     }
 528
 529     /// Pretty-print an item
 530     pub fn print_item(&mut self, item: &hir::Item) -> io::Result<()> {
 531         self.hardbreak_if_not_bol()?;
 532         self.maybe_print_comment(item.span.lo())?;
 533         self.print_outer_attributes(&item.attrs)?;
 534         self.ann.pre(self, NodeItem(item))?;
 535         match item.node {
 536             hir::ItemExternCrate(ref optional_path) => {
 537                 self.head(&visibility_qualified(&item.vis, "extern crate"))?;
 538                 if let Some(p) = *optional_path {
 539                     let val = p.as_str();
 540                     if val.contains("-") {
 541                         self.print_string(&val, ast::StrStyle::Cooked)?;
 542                     } else {
 543                         self.print_name(p)?;
 544                     }
 545                     self.s.space()?;
 546                     self.s.word("as")?;
 547                     self.s.space()?;
 548                 }
 549                 self.print_name(item.name)?;
 550                 self.s.word(";")?;
 551                 self.end()?; // end inner head-block
 552                 self.end()?; // end outer head-block
 553             }
 554             hir::ItemUse(ref path, kind) => {
 555                 self.head(&visibility_qualified(&item.vis, "use"))?;
 556                 self.print_path(path, false)?;
 557
 558                 match kind {
 559                     hir::UseKind::Single => {
 560                         if path.segments.last().unwrap().name != item.name {
 561                             self.s.space()?;
 562                             self.word_space("as")?;
 563                             self.print_name(item.name)?;
 564                         }
 565                         self.s.word(";")?;
 566                     }
 567                     hir::UseKind::Glob => self.s.word("::*;")?,
 568                     hir::UseKind::ListStem => self.s.word("::{};")?
 569                 }
 570                 self.end()?; // end inner head-block
 571                 self.end()?; // end outer head-block
 572             }
 573             hir::ItemStatic(ref ty, m, expr) => {
 574                 self.head(&visibility_qualified(&item.vis, "static"))?;
 575                 if m == hir::MutMutable {
 576                     self.word_space("mut")?;
 577                 }
 578                 self.print_name(item.name)?;
 579                 self.word_space(":")?;
 580                 self.print_type(&ty)?;
 581                 self.s.space()?;
 582                 self.end()?; // end the head-ibox
 583
 584                 self.word_space("=")?;
 585                 self.ann.nested(self, Nested::Body(expr))?;
 586                 self.s.word(";")?;
 587                 self.end()?; // end the outer cbox
 588             }
 589             hir::ItemConst(ref ty, expr) => {
 590                 self.head(&visibility_qualified(&item.vis, "const"))?;
 591                 self.print_name(item.name)?;
 592                 self.word_space(":")?;
 593                 self.print_type(&ty)?;
 594                 self.s.space()?;
 595                 self.end()?; // end the head-ibox
 596
 597                 self.word_space("=")?;
 598                 self.ann.nested(self, Nested::Body(expr))?;
 599                 self.s.word(";")?;
 600                 self.end()?; // end the outer cbox
 601             }
 602             hir::ItemFn(ref decl, unsafety, constness, abi, ref typarams, body) => {
 603                 self.head("")?;
 604                 self.print_fn(decl,
 605                               unsafety,
 606                               constness,
 607                               abi,
 608                               Some(item.name),
 609                               typarams,
 610                               &item.vis,
 611                               &[],
 612                               Some(body))?;
 613                 self.s.word(" ")?;
 614                 self.end()?; // need to close a box
 615                 self.end()?; // need to close a box
 616                 self.ann.nested(self, Nested::Body(body))?;
 617             }
 618             hir::ItemMod(ref _mod) => {
 619                 self.head(&visibility_qualified(&item.vis, "mod"))?;
 620                 self.print_name(item.name)?;
 621                 self.nbsp()?;
 622                 self.bopen()?;
 623                 self.print_mod(_mod, &item.attrs)?;
 624                 self.bclose(item.span)?;
 625             }
 626             hir::ItemForeignMod(ref nmod) => {
 627                 self.head("extern")?;
 628                 self.word_nbsp(&nmod.abi.to_string())?;
 629                 self.bopen()?;
 630                 self.print_foreign_mod(nmod, &item.attrs)?;
 631                 self.bclose(item.span)?;
 632             }
 633             hir::ItemGlobalAsm(ref ga) => {
 634                 self.head(&visibility_qualified(&item.vis, "global asm"))?;
 635                 self.s.word(&ga.asm.as_str())?;
 636                 self.end()?
 637             }
 638             hir::ItemTy(ref ty, ref params) => {
 639                 self.ibox(indent_unit)?;
 640                 self.ibox(0)?;
 641                 self.word_nbsp(&visibility_qualified(&item.vis, "type"))?;
 642                 self.print_name(item.name)?;
 643                 self.print_generics(params)?;
 644                 self.end()?; // end the inner ibox
 645
 646                 self.print_where_clause(&params.where_clause)?;
 647                 self.s.space()?;
 648                 self.word_space("=")?;
 649                 self.print_type(&ty)?;
 650                 self.s.word(";")?;
 651                 self.end()?; // end the outer ibox
 652             }
 653             hir::ItemEnum(ref enum_definition, ref params) => {
 654                 self.print_enum_def(enum_definition, params, item.name, item.span, &item.vis)?;
 655             }
 656             hir::ItemStruct(ref struct_def, ref generics) => {
 657                 self.head(&visibility_qualified(&item.vis, "struct"))?;
 658                 self.print_struct(struct_def, generics, item.name, item.span, true)?;
 659             }
 660             hir::ItemUnion(ref struct_def, ref generics) => {
 661                 self.head(&visibility_qualified(&item.vis, "union"))?;
 662                 self.print_struct(struct_def, generics, item.name, item.span, true)?;
 663             }
 664             hir::ItemAutoImpl(unsafety, ref trait_ref) => {
 665                 self.head("")?;
 666                 self.print_visibility(&item.vis)?;
 667                 self.print_unsafety(unsafety)?;
 668                 self.word_nbsp("impl")?;
 669                 self.print_trait_ref(trait_ref)?;
 670                 self.s.space()?;
 671                 self.word_space("for")?;
 672                 self.word_space("..")?;
 673                 self.bopen()?;
 674                 self.bclose(item.span)?;
 675             }
 676             hir::ItemImpl(unsafety,
 677                           polarity,
 678                           defaultness,
 679                           ref generics,
 680                           ref opt_trait,
 681                           ref ty,
 682                           ref impl_items) => {
 683                 self.head("")?;
 684                 self.print_visibility(&item.vis)?;
 685                 self.print_defaultness(defaultness)?;
 686                 self.print_unsafety(unsafety)?;
 687                 self.word_nbsp("impl")?;
 688
 689                 if generics.is_parameterized() {
 690                     self.print_generics(generics)?;
 691                     self.s.space()?;
 692                 }
 693
 694                 match polarity {
 695                     hir::ImplPolarity::Negative => {
 696                         self.s.word("!")?;
 697                     }
 698                     _ => {}
 699                 }
 700
 701                 match opt_trait {
 702                     &Some(ref t) => {
 703                         self.print_trait_ref(t)?;
 704                         self.s.space()?;
 705                         self.word_space("for")?;
 706                     }
 707                     &None => {}
 708                 }
 709
 710                 self.print_type(&ty)?;
 711                 self.print_where_clause(&generics.where_clause)?;
 712
 713                 self.s.space()?;
 714                 self.bopen()?;
 715                 self.print_inner_attributes(&item.attrs)?;
 716                 for impl_item in impl_items {
 717                     self.ann.nested(self, Nested::ImplItem(impl_item.id))?;
 718                 }
 719                 self.bclose(item.span)?;
 720             }
 721             hir::ItemTrait(is_auto, unsafety, ref generics, ref bounds, ref trait_items) => {
 722                 self.head("")?;
 723                 self.print_visibility(&item.vis)?;
 724                 self.print_is_auto(is_auto)?;
 725                 self.print_unsafety(unsafety)?;
 726                 self.word_nbsp("trait")?;
 727                 self.print_name(item.name)?;
 728                 self.print_generics(generics)?;
 729                 let mut real_bounds = Vec::with_capacity(bounds.len());
 730                 for b in bounds.iter() {
 731                     if let TraitTyParamBound(ref ptr, hir::TraitBoundModifier::Maybe) = *b {
 732                         self.s.space()?;
 733                         self.word_space("for ?")?;
 734                         self.print_trait_ref(&ptr.trait_ref)?;
 735                     } else {
 736                         real_bounds.push(b.clone());
 737                     }
 738                 }
 739                 self.print_bounds(":", &real_bounds[..])?;
 740                 self.print_where_clause(&generics.where_clause)?;
 741                 self.s.word(" ")?;
 742                 self.bopen()?;
 743                 for trait_item in trait_items {
 744                     self.ann.nested(self, Nested::TraitItem(trait_item.id))?;
 745                 }
 746                 self.bclose(item.span)?;
 747             }
 748         }
 749         self.ann.post(self, NodeItem(item))
 750     }
 751
 752     pub fn print_trait_ref(&mut self, t: &hir::TraitRef) -> io::Result<()> {
 753         self.print_path(&t.path, false)
 754     }
 755
 756     fn print_formal_lifetime_list(&mut self, lifetimes: &[hir::LifetimeDef]) -> io::Result<()> {
 757         if !lifetimes.is_empty() {
 758             self.s.word("for<")?;
 759             let mut comma = false;
 760             for lifetime_def in lifetimes {
 761                 if comma {
 762                     self.word_space(",")?
 763                 }
 764                 self.print_lifetime_def(lifetime_def)?;
 765                 comma = true;
 766             }
 767             self.s.word(">")?;
 768         }
 769         Ok(())
 770     }
 771
 772     fn print_poly_trait_ref(&mut self, t: &hir::PolyTraitRef) -> io::Result<()> {
 773         self.print_formal_lifetime_list(&t.bound_lifetimes)?;
 774         self.print_trait_ref(&t.trait_ref)
 775     }
 776
 777     pub fn print_enum_def(&mut self,
 778                           enum_definition: &hir::EnumDef,
 779                           generics: &hir::Generics,
 780                           name: ast::Name,
 781                           span: syntax_pos::Span,
 782                           visibility: &hir::Visibility)
 783                           -> io::Result<()> {
 784         self.head(&visibility_qualified(visibility, "enum"))?;
 785         self.print_name(name)?;
 786         self.print_generics(generics)?;
 787         self.print_where_clause(&generics.where_clause)?;
 788         self.s.space()?;
 789         self.print_variants(&enum_definition.variants, span)
 790     }
 791
 792     pub fn print_variants(&mut self,
 793                           variants: &[hir::Variant],
 794                           span: syntax_pos::Span)
 795                           -> io::Result<()> {
 796         self.bopen()?;
 797         for v in variants {
 798             self.space_if_not_bol()?;
 799             self.maybe_print_comment(v.span.lo())?;
 800             self.print_outer_attributes(&v.node.attrs)?;
 801             self.ibox(indent_unit)?;
 802             self.print_variant(v)?;
 803             self.s.word(",")?;
 804             self.end()?;
 805             self.maybe_print_trailing_comment(v.span, None)?;
 806         }
 807         self.bclose(span)
 808     }
 809
 810     pub fn print_visibility(&mut self, vis: &hir::Visibility) -> io::Result<()> {
 811         match *vis {
 812             hir::Public => self.word_nbsp("pub"),
 813             hir::Visibility::Crate => self.word_nbsp("pub(crate)"),
 814             hir::Visibility::Restricted { ref path, .. } => {
 815                 self.s.word("pub(")?;
 816                 self.print_path(path, false)?;
 817                 self.word_nbsp(")")
 818             }
 819             hir::Inherited => Ok(()),
 820         }
 821     }
 822
 823     pub fn print_defaultness(&mut self, defaultness: hir::Defaultness) -> io::Result<()> {
 824         match defaultness {
 825             hir::Defaultness::Default { .. } => self.word_nbsp("default")?,
 826             hir::Defaultness::Final => (),
 827         }
 828         Ok(())
 829     }
 830
 831     pub fn print_struct(&mut self,
 832                         struct_def: &hir::VariantData,
 833                         generics: &hir::Generics,
 834                         name: ast::Name,
 835                         span: syntax_pos::Span,
 836                         print_finalizer: bool)
 837                         -> io::Result<()> {
 838         self.print_name(name)?;
 839         self.print_generics(generics)?;
 840         if !struct_def.is_struct() {
 841             if struct_def.is_tuple() {
 842                 self.popen()?;
 843                 self.commasep(Inconsistent, struct_def.fields(), |s, field| {
 844                     s.maybe_print_comment(field.span.lo())?;
 845                     s.print_outer_attributes(&field.attrs)?;
 846                     s.print_visibility(&field.vis)?;
 847                     s.print_type(&field.ty)
 848                 })?;
 849                 self.pclose()?;
 850             }
 851             self.print_where_clause(&generics.where_clause)?;
 852             if print_finalizer {
 853                 self.s.word(";")?;
 854             }
 855             self.end()?;
 856             self.end() // close the outer-box
 857         } else {
 858             self.print_where_clause(&generics.where_clause)?;
 859             self.nbsp()?;
 860             self.bopen()?;
 861             self.hardbreak_if_not_bol()?;
 862
 863             for field in struct_def.fields() {
 864                 self.hardbreak_if_not_bol()?;
 865                 self.maybe_print_comment(field.span.lo())?;
 866                 self.print_outer_attributes(&field.attrs)?;
 867                 self.print_visibility(&field.vis)?;
 868                 self.print_name(field.name)?;
 869                 self.word_nbsp(":")?;
 870                 self.print_type(&field.ty)?;
 871                 self.s.word(",")?;
 872             }
 873
 874             self.bclose(span)
 875         }
 876     }
 877
 878     pub fn print_variant(&mut self, v: &hir::Variant) -> io::Result<()> {
 879         self.head("")?;
 880         let generics = hir::Generics::empty();
 881         self.print_struct(&v.node.data, &generics, v.node.name, v.span, false)?;
 882         if let Some(d) = v.node.disr_expr {
 883             self.s.space()?;
 884             self.word_space("=")?;
 885             self.ann.nested(self, Nested::Body(d))?;
 886         }
 887         Ok(())
 888     }
 889     pub fn print_method_sig(&mut self,
 890                             name: ast::Name,
 891                             m: &hir::MethodSig,
 892                             generics: &hir::Generics,
 893                             vis: &hir::Visibility,
 894                             arg_names: &[Spanned<ast::Name>],
 895                             body_id: Option<hir::BodyId>)
 896                             -> io::Result<()> {
 897         self.print_fn(&m.decl,
 898                       m.unsafety,
 899                       m.constness,
 900                       m.abi,
 901                       Some(name),
 902                       generics,
 903                       vis,
 904                       arg_names,
 905                       body_id)
 906     }
 907
 908     pub fn print_trait_item(&mut self, ti: &hir::TraitItem) -> io::Result<()> {
 909         self.ann.pre(self, NodeSubItem(ti.id))?;
 910         self.hardbreak_if_not_bol()?;
 911         self.maybe_print_comment(ti.span.lo())?;
 912         self.print_outer_attributes(&ti.attrs)?;
 913         match ti.node {
 914             hir::TraitItemKind::Const(ref ty, default) => {
 915                 self.print_associated_const(ti.name, &ty, default, &hir::Inherited)?;
 916             }
 917             hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Required(ref arg_names)) => {
 918                 self.print_method_sig(ti.name, sig, &ti.generics, &hir::Inherited, arg_names,
 919                     None)?;
 920                 self.s.word(";")?;
 921             }
 922             hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Provided(body)) => {
 923                 self.head("")?;
 924                 self.print_method_sig(ti.name, sig, &ti.generics, &hir::Inherited, &[],
 925                     Some(body))?;
 926                 self.nbsp()?;
 927                 self.end()?; // need to close a box
 928                 self.end()?; // need to close a box
 929                 self.ann.nested(self, Nested::Body(body))?;
 930             }
 931             hir::TraitItemKind::Type(ref bounds, ref default) => {
 932                 self.print_associated_type(ti.name,
 933                                            Some(bounds),
 934                                            default.as_ref().map(|ty| &**ty))?;
 935             }
 936         }
 937         self.ann.post(self, NodeSubItem(ti.id))
 938     }
 939
 940     pub fn print_impl_item(&mut self, ii: &hir::ImplItem) -> io::Result<()> {
 941         self.ann.pre(self, NodeSubItem(ii.id))?;
 942         self.hardbreak_if_not_bol()?;
 943         self.maybe_print_comment(ii.span.lo())?;
 944         self.print_outer_attributes(&ii.attrs)?;
 945         self.print_defaultness(ii.defaultness)?;
 946
 947         match ii.node {
 948             hir::ImplItemKind::Const(ref ty, expr) => {
 949                 self.print_associated_const(ii.name, &ty, Some(expr), &ii.vis)?;
 950             }
 951             hir::ImplItemKind::Method(ref sig, body) => {
 952                 self.head("")?;
 953                 self.print_method_sig(ii.name, sig, &ii.generics, &ii.vis, &[], Some(body))?;
 954                 self.nbsp()?;
 955                 self.end()?; // need to close a box
 956                 self.end()?; // need to close a box
 957                 self.ann.nested(self, Nested::Body(body))?;
 958             }
 959             hir::ImplItemKind::Type(ref ty) => {
 960                 self.print_associated_type(ii.name, None, Some(ty))?;
 961             }
 962         }
 963         self.ann.post(self, NodeSubItem(ii.id))
 964     }
 965
 966     pub fn print_stmt(&mut self, st: &hir::Stmt) -> io::Result<()> {
 967         self.maybe_print_comment(st.span.lo())?;
 968         match st.node {
 969             hir::StmtDecl(ref decl, _) => {
 970                 self.print_decl(&decl)?;
 971             }
 972             hir::StmtExpr(ref expr, _) => {
 973                 self.space_if_not_bol()?;
 974                 self.print_expr(&expr)?;
 975             }
 976             hir::StmtSemi(ref expr, _) => {
 977                 self.space_if_not_bol()?;
 978                 self.print_expr(&expr)?;
 979                 self.s.word(";")?;
 980             }
 981         }
 982         if stmt_ends_with_semi(&st.node) {
 983             self.s.word(";")?;
 984         }
 985         self.maybe_print_trailing_comment(st.span, None)
 986     }
 987
 988     pub fn print_block(&mut self, blk: &hir::Block) -> io::Result<()> {
 989         self.print_block_with_attrs(blk, &[])
 990     }
 991
 992     pub fn print_block_unclosed(&mut self, blk: &hir::Block) -> io::Result<()> {
 993         self.print_block_unclosed_indent(blk, indent_unit)
 994     }
 995
 996     pub fn print_block_unclosed_indent(&mut self,
 997                                        blk: &hir::Block,
 998                                        indented: usize)
 999                                        -> io::Result<()> {
1000         self.print_block_maybe_unclosed(blk, indented, &[], false)
1001     }
1002
1003     pub fn print_block_with_attrs(&mut self,
1004                                   blk: &hir::Block,
1005                                   attrs: &[ast::Attribute])
1006                                   -> io::Result<()> {
1007         self.print_block_maybe_unclosed(blk, indent_unit, attrs, true)
1008     }
1009
1010     pub fn print_block_maybe_unclosed(&mut self,
1011                                       blk: &hir::Block,
1012                                       indented: usize,
1013                                       attrs: &[ast::Attribute],
1014                                       close_box: bool)
1015                                       -> io::Result<()> {
1016         match blk.rules {
1017             hir::UnsafeBlock(..) => self.word_space("unsafe")?,
1018             hir::PushUnsafeBlock(..) => self.word_space("push_unsafe")?,
1019             hir::PopUnsafeBlock(..) => self.word_space("pop_unsafe")?,
1020             hir::DefaultBlock => (),
1021         }
1022         self.maybe_print_comment(blk.span.lo())?;
1023         self.ann.pre(self, NodeBlock(blk))?;
1024         self.bopen()?;
1025
1026         self.print_inner_attributes(attrs)?;
1027
1028         for st in &blk.stmts {
1029             self.print_stmt(st)?;
1030         }
1031         match blk.expr {
1032             Some(ref expr) => {
1033                 self.space_if_not_bol()?;
1034                 self.print_expr(&expr)?;
1035                 self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi()))?;
1036             }
1037             _ => (),
1038         }
1039         self.bclose_maybe_open(blk.span, indented, close_box)?;
1040         self.ann.post(self, NodeBlock(blk))
1041     }
1042
1043     fn print_else(&mut self, els: Option<&hir::Expr>) -> io::Result<()> {
1044         match els {
1045             Some(_else) => {
1046                 match _else.node {
1047                     // "another else-if"
1048                     hir::ExprIf(ref i, ref then, ref e) => {
1049                         self.cbox(indent_unit - 1)?;
1050                         self.ibox(0)?;
1051                         self.s.word(" else if ")?;
1052                         self.print_expr_as_cond(&i)?;
1053                         self.s.space()?;
1054                         self.print_expr(&then)?;
1055                         self.print_else(e.as_ref().map(|e| &**e))
1056                     }
1057                     // "final else"
1058                     hir::ExprBlock(ref b) => {
1059                         self.cbox(indent_unit - 1)?;
1060                         self.ibox(0)?;
1061                         self.s.word(" else ")?;
1062                         self.print_block(&b)
1063                     }
1064                     // BLEAH, constraints would be great here
1065                     _ => {
1066                         panic!("print_if saw if with weird alternative");
1067                     }
1068                 }
1069             }
1070             _ => Ok(()),
1071         }
1072     }
1073
1074     pub fn print_if(&mut self,
1075                     test: &hir::Expr,
1076                     blk: &hir::Expr,
1077                     elseopt: Option<&hir::Expr>)
1078                     -> io::Result<()> {
1079         self.head("if")?;
1080         self.print_expr_as_cond(test)?;
1081         self.s.space()?;
1082         self.print_expr(blk)?;
1083         self.print_else(elseopt)
1084     }
1085
1086     pub fn print_if_let(&mut self,
1087                         pat: &hir::Pat,
1088                         expr: &hir::Expr,
1089                         blk: &hir::Block,
1090                         elseopt: Option<&hir::Expr>)
1091                         -> io::Result<()> {
1092         self.head("if let")?;
1093         self.print_pat(pat)?;
1094         self.s.space()?;
1095         self.word_space("=")?;
1096         self.print_expr_as_cond(expr)?;
1097         self.s.space()?;
1098         self.print_block(blk)?;
1099         self.print_else(elseopt)
1100     }
1101
1102
1103     fn print_call_post(&mut self, args: &[hir::Expr]) -> io::Result<()> {
1104         self.popen()?;
1105         self.commasep_exprs(Inconsistent, args)?;
1106         self.pclose()
1107     }
1108
1109     pub fn print_expr_maybe_paren(&mut self, expr: &hir::Expr, prec: i8) -> io::Result<()> {
1110         let needs_par = expr_precedence(expr) < prec;
1111         if needs_par {
1112             self.popen()?;
1113         }
1114         self.print_expr(expr)?;
1115         if needs_par {
1116             self.pclose()?;
1117         }
1118         Ok(())
1119     }
1120
1121     /// Print an expr using syntax that's acceptable in a condition position, such as the `cond` in
1122     /// `if cond { ... }`.
1123     pub fn print_expr_as_cond(&mut self, expr: &hir::Expr) -> io::Result<()> {
1124         let needs_par = match expr.node {
1125             // These cases need parens due to the parse error observed in #26461: `if return {}`
1126             // parses as the erroneous construct `if (return {})`, not `if (return) {}`.
1127             hir::ExprClosure(..) |
1128             hir::ExprRet(..) |
1129             hir::ExprBreak(..) => true,
1130
1131             _ => contains_exterior_struct_lit(expr),
1132         };
1133
1134         if needs_par {
1135             self.popen()?;
1136         }
1137         self.print_expr(expr)?;
1138         if needs_par {
1139             self.pclose()?;
1140         }
1141         Ok(())
1142     }
1143
1144     fn print_expr_vec(&mut self, exprs: &[hir::Expr]) -> io::Result<()> {
1145         self.ibox(indent_unit)?;
1146         self.s.word("[")?;
1147         self.commasep_exprs(Inconsistent, exprs)?;
1148         self.s.word("]")?;
1149         self.end()
1150     }
1151
1152     fn print_expr_repeat(&mut self, element: &hir::Expr, count: hir::BodyId) -> io::Result<()> {
1153         self.ibox(indent_unit)?;
1154         self.s.word("[")?;
1155         self.print_expr(element)?;
1156         self.word_space(";")?;
1157         self.ann.nested(self, Nested::Body(count))?;
1158         self.s.word("]")?;
1159         self.end()
1160     }
1161
1162     fn print_expr_struct(&mut self,
1163                          qpath: &hir::QPath,
1164                          fields: &[hir::Field],
1165                          wth: &Option<P<hir::Expr>>)
1166                          -> io::Result<()> {
1167         self.print_qpath(qpath, true)?;
1168         self.s.word("{")?;
1169         self.commasep_cmnt(Consistent,
1170                            &fields[..],
1171                            |s, field| {
1172                                s.ibox(indent_unit)?;
1173                                if !field.is_shorthand {
1174                                     s.print_name(field.name.node)?;
1175                                     s.word_space(":")?;
1176                                }
1177                                s.print_expr(&field.expr)?;
1178                                s.end()
1179                            },
1180                            |f| f.span)?;
1181         match *wth {
1182             Some(ref expr) => {
1183                 self.ibox(indent_unit)?;
1184                 if !fields.is_empty() {
1185                     self.s.word(",")?;
1186                     self.s.space()?;
1187                 }
1188                 self.s.word("..")?;
1189                 self.print_expr(&expr)?;
1190                 self.end()?;
1191             }
1192             _ => if !fields.is_empty() {
1193                 self.s.word(",")?
1194             },
1195         }
1196         self.s.word("}")?;
1197         Ok(())
1198     }
1199
1200     fn print_expr_tup(&mut self, exprs: &[hir::Expr]) -> io::Result<()> {
1201         self.popen()?;
1202         self.commasep_exprs(Inconsistent, exprs)?;
1203         if exprs.len() == 1 {
1204             self.s.word(",")?;
1205         }
1206         self.pclose()
1207     }
1208
1209     fn print_expr_call(&mut self, func: &hir::Expr, args: &[hir::Expr]) -> io::Result<()> {
1210         let prec =
1211             match func.node {
1212                 hir::ExprField(..) |
1213                 hir::ExprTupField(..) => parser::PREC_FORCE_PAREN,
1214                 _ => parser::PREC_POSTFIX,
1215             };
1216
1217         self.print_expr_maybe_paren(func, prec)?;
1218         self.print_call_post(args)
1219     }
1220
1221     fn print_expr_method_call(&mut self,
1222                               segment: &hir::PathSegment,
1223                               args: &[hir::Expr])
1224                               -> io::Result<()> {
1225         let base_args = &args[1..];
1226         self.print_expr_maybe_paren(&args[0], parser::PREC_POSTFIX)?;
1227         self.s.word(".")?;
1228         self.print_name(segment.name)?;
1229
1230         segment.with_parameters(|parameters| {
1231             if !parameters.lifetimes.is_empty() ||
1232                 !parameters.types.is_empty() ||
1233                 !parameters.bindings.is_empty()
1234             {
1235                 self.print_path_parameters(&parameters, segment.infer_types, true)
1236             } else {
1237                 Ok(())
1238             }
1239         })?;
1240         self.print_call_post(base_args)
1241     }
1242
1243     fn print_expr_binary(&mut self,
1244                          op: hir::BinOp,
1245                          lhs: &hir::Expr,
1246                          rhs: &hir::Expr)
1247                          -> io::Result<()> {
1248         let assoc_op = bin_op_to_assoc_op(op.node);
1249         let prec = assoc_op.precedence() as i8;
1250         let fixity = assoc_op.fixity();
1251
1252         let (left_prec, right_prec) = match fixity {
1253             Fixity::Left => (prec, prec + 1),
1254             Fixity::Right => (prec + 1, prec),
1255             Fixity::None => (prec + 1, prec + 1),
1256         };
1257
1258         let left_prec = match (&lhs.node, op.node) {
1259             // These cases need parens: `x as i32 < y` has the parser thinking that `i32 < y` is
1260             // the beginning of a path type. It starts trying to parse `x as (i32 < y ...` instead
1261             // of `(x as i32) < ...`. We need to convince it _not_ to do that.
1262             (&hir::ExprCast { .. }, hir::BinOp_::BiLt) |
1263             (&hir::ExprCast { .. }, hir::BinOp_::BiShl) => parser::PREC_FORCE_PAREN,
1264             _ => left_prec,
1265         };
1266
1267         self.print_expr_maybe_paren(lhs, left_prec)?;
1268         self.s.space()?;
1269         self.word_space(op.node.as_str())?;
1270         self.print_expr_maybe_paren(rhs, right_prec)
1271     }
1272
1273     fn print_expr_unary(&mut self, op: hir::UnOp, expr: &hir::Expr) -> io::Result<()> {
1274         self.s.word(op.as_str())?;
1275         self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
1276     }
1277
1278     fn print_expr_addr_of(&mut self,
1279                           mutability: hir::Mutability,
1280                           expr: &hir::Expr)
1281                           -> io::Result<()> {
1282         self.s.word("&")?;
1283         self.print_mutability(mutability)?;
1284         self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
1285     }
1286
1287     pub fn print_expr(&mut self, expr: &hir::Expr) -> io::Result<()> {
1288         self.maybe_print_comment(expr.span.lo())?;
1289         self.print_outer_attributes(&expr.attrs)?;
1290         self.ibox(indent_unit)?;
1291         self.ann.pre(self, NodeExpr(expr))?;
1292         match expr.node {
1293             hir::ExprBox(ref expr) => {
1294                 self.word_space("box")?;
1295                 self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)?;
1296             }
1297             hir::ExprArray(ref exprs) => {
1298                 self.print_expr_vec(exprs)?;
1299             }
1300             hir::ExprRepeat(ref element, count) => {
1301                 self.print_expr_repeat(&element, count)?;
1302             }
1303             hir::ExprStruct(ref qpath, ref fields, ref wth) => {
1304                 self.print_expr_struct(qpath, &fields[..], wth)?;
1305             }
1306             hir::ExprTup(ref exprs) => {
1307                 self.print_expr_tup(exprs)?;
1308             }
1309             hir::ExprCall(ref func, ref args) => {
1310                 self.print_expr_call(&func, args)?;
1311             }
1312             hir::ExprMethodCall(ref segment, _, ref args) => {
1313                 self.print_expr_method_call(segment, args)?;
1314             }
1315             hir::ExprBinary(op, ref lhs, ref rhs) => {
1316                 self.print_expr_binary(op, &lhs, &rhs)?;
1317             }
1318             hir::ExprUnary(op, ref expr) => {
1319                 self.print_expr_unary(op, &expr)?;
1320             }
1321             hir::ExprAddrOf(m, ref expr) => {
1322                 self.print_expr_addr_of(m, &expr)?;
1323             }
1324             hir::ExprLit(ref lit) => {
1325                 self.print_literal(&lit)?;
1326             }
1327             hir::ExprCast(ref expr, ref ty) => {
1328                 let prec = AssocOp::As.precedence() as i8;
1329                 self.print_expr_maybe_paren(&expr, prec)?;
1330                 self.s.space()?;
1331                 self.word_space("as")?;
1332                 self.print_type(&ty)?;
1333             }
1334             hir::ExprType(ref expr, ref ty) => {
1335                 let prec = AssocOp::Colon.precedence() as i8;
1336                 self.print_expr_maybe_paren(&expr, prec)?;
1337                 self.word_space(":")?;
1338                 self.print_type(&ty)?;
1339             }
1340             hir::ExprIf(ref test, ref blk, ref elseopt) => {
1341                 self.print_if(&test, &blk, elseopt.as_ref().map(|e| &**e))?;
1342             }
1343             hir::ExprWhile(ref test, ref blk, opt_sp_name) => {
1344                 if let Some(sp_name) = opt_sp_name {
1345                     self.print_name(sp_name.node)?;
1346                     self.word_space(":")?;
1347                 }
1348                 self.head("while")?;
1349                 self.print_expr_as_cond(&test)?;
1350                 self.s.space()?;
1351                 self.print_block(&blk)?;
1352             }
1353             hir::ExprLoop(ref blk, opt_sp_name, _) => {
1354                 if let Some(sp_name) = opt_sp_name {
1355                     self.print_name(sp_name.node)?;
1356                     self.word_space(":")?;
1357                 }
1358                 self.head("loop")?;
1359                 self.s.space()?;
1360                 self.print_block(&blk)?;
1361             }
1362             hir::ExprMatch(ref expr, ref arms, _) => {
1363                 self.cbox(indent_unit)?;
1364                 self.ibox(4)?;
1365                 self.word_nbsp("match")?;
1366                 self.print_expr_as_cond(&expr)?;
1367                 self.s.space()?;
1368                 self.bopen()?;
1369                 for arm in arms {
1370                     self.print_arm(arm)?;
1371                 }
1372                 self.bclose_(expr.span, indent_unit)?;
1373             }
1374             hir::ExprClosure(capture_clause, ref decl, body, _fn_decl_span, _gen) => {
1375                 self.print_capture_clause(capture_clause)?;
1376
1377                 self.print_closure_args(&decl, body)?;
1378                 self.s.space()?;
1379
1380                 // this is a bare expression
1381                 self.ann.nested(self, Nested::Body(body))?;
1382                 self.end()?; // need to close a box
1383
1384                 // a box will be closed by print_expr, but we didn't want an overall
1385                 // wrapper so we closed the corresponding opening. so create an
1386                 // empty box to satisfy the close.
1387                 self.ibox(0)?;
1388             }
1389             hir::ExprBlock(ref blk) => {
1390                 // containing cbox, will be closed by print-block at }
1391                 self.cbox(indent_unit)?;
1392                 // head-box, will be closed by print-block after {
1393                 self.ibox(0)?;
1394                 self.print_block(&blk)?;
1395             }
1396             hir::ExprAssign(ref lhs, ref rhs) => {
1397                 let prec = AssocOp::Assign.precedence() as i8;
1398                 self.print_expr_maybe_paren(&lhs, prec + 1)?;
1399                 self.s.space()?;
1400                 self.word_space("=")?;
1401                 self.print_expr_maybe_paren(&rhs, prec)?;
1402             }
1403             hir::ExprAssignOp(op, ref lhs, ref rhs) => {
1404                 let prec = AssocOp::Assign.precedence() as i8;
1405                 self.print_expr_maybe_paren(&lhs, prec + 1)?;
1406                 self.s.space()?;
1407                 self.s.word(op.node.as_str())?;
1408                 self.word_space("=")?;
1409                 self.print_expr_maybe_paren(&rhs, prec)?;
1410             }
1411             hir::ExprField(ref expr, name) => {
1412                 self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX)?;
1413                 self.s.word(".")?;
1414                 self.print_name(name.node)?;
1415             }
1416             hir::ExprTupField(ref expr, id) => {
1417                 self.print_expr_maybe_paren(&expr, parser::PREC_POSTFIX)?;
1418                 self.s.word(".")?;
1419                 self.print_usize(id.node)?;
1420             }
1421             hir::ExprIndex(ref expr, ref index) => {
1422                 self.print_expr_maybe_paren(&expr, parser::PREC_POSTFIX)?;
1423                 self.s.word("[")?;
1424                 self.print_expr(&index)?;
1425                 self.s.word("]")?;
1426             }
1427             hir::ExprPath(ref qpath) => {
1428                 self.print_qpath(qpath, true)?
1429             }
1430             hir::ExprBreak(label, ref opt_expr) => {
1431                 self.s.word("break")?;
1432                 self.s.space()?;
1433                 if let Some(label_ident) = label.ident {
1434                     self.print_name(label_ident.node.name)?;
1435                     self.s.space()?;
1436                 }
1437                 if let Some(ref expr) = *opt_expr {
1438                     self.print_expr_maybe_paren(expr, parser::PREC_JUMP)?;
1439                     self.s.space()?;
1440                 }
1441             }
1442             hir::ExprAgain(label) => {
1443                 self.s.word("continue")?;
1444                 self.s.space()?;
1445                 if let Some(label_ident) = label.ident {
1446                     self.print_name(label_ident.node.name)?;
1447                     self.s.space()?
1448                 }
1449             }
1450             hir::ExprRet(ref result) => {
1451                 self.s.word("return")?;
1452                 match *result {
1453                     Some(ref expr) => {
1454                         self.s.word(" ")?;
1455                         self.print_expr_maybe_paren(&expr, parser::PREC_JUMP)?;
1456                     }
1457                     _ => (),
1458                 }
1459             }
1460             hir::ExprInlineAsm(ref a, ref outputs, ref inputs) => {
1461                 self.s.word("asm!")?;
1462                 self.popen()?;
1463                 self.print_string(&a.asm.as_str(), a.asm_str_style)?;
1464                 self.word_space(":")?;
1465
1466                 let mut out_idx = 0;
1467                 self.commasep(Inconsistent, &a.outputs, |s, out| {
1468                     let constraint = out.constraint.as_str();
1469                     let mut ch = constraint.chars();
1470                     match ch.next() {
1471                         Some('=') if out.is_rw => {
1472                             s.print_string(&format!("+{}", ch.as_str()),
1473                                            ast::StrStyle::Cooked)?
1474                         }
1475                         _ => s.print_string(&constraint, ast::StrStyle::Cooked)?,
1476                     }
1477                     s.popen()?;
1478                     s.print_expr(&outputs[out_idx])?;
1479                     s.pclose()?;
1480                     out_idx += 1;
1481                     Ok(())
1482                 })?;
1483                 self.s.space()?;
1484                 self.word_space(":")?;
1485
1486                 let mut in_idx = 0;
1487                 self.commasep(Inconsistent, &a.inputs, |s, co| {
1488                     s.print_string(&co.as_str(), ast::StrStyle::Cooked)?;
1489                     s.popen()?;
1490                     s.print_expr(&inputs[in_idx])?;
1491                     s.pclose()?;
1492                     in_idx += 1;
1493                     Ok(())
1494                 })?;
1495                 self.s.space()?;
1496                 self.word_space(":")?;
1497
1498                 self.commasep(Inconsistent, &a.clobbers, |s, co| {
1499                     s.print_string(&co.as_str(), ast::StrStyle::Cooked)?;
1500                     Ok(())
1501                 })?;
1502
1503                 let mut options = vec![];
1504                 if a.volatile {
1505                     options.push("volatile");
1506                 }
1507                 if a.alignstack {
1508                     options.push("alignstack");
1509                 }
1510                 if a.dialect == ast::AsmDialect::Intel {
1511                     options.push("intel");
1512                 }
1513
1514                 if !options.is_empty() {
1515                     self.s.space()?;
1516                     self.word_space(":")?;
1517                     self.commasep(Inconsistent, &options, |s, &co| {
1518                         s.print_string(co, ast::StrStyle::Cooked)?;
1519                         Ok(())
1520                     })?;
1521                 }
1522
1523                 self.pclose()?;
1524             }
1525             hir::ExprYield(ref expr) => {
1526                 self.word_space("yield")?;
1527                 self.print_expr_maybe_paren(&expr, parser::PREC_JUMP)?;
1528             }
1529         }
1530         self.ann.post(self, NodeExpr(expr))?;
1531         self.end()
1532     }
1533
1534     pub fn print_local_decl(&mut self, loc: &hir::Local) -> io::Result<()> {
1535         self.print_pat(&loc.pat)?;
1536         if let Some(ref ty) = loc.ty {
1537             self.word_space(":")?;
1538             self.print_type(&ty)?;
1539         }
1540         Ok(())
1541     }
1542
1543     pub fn print_decl(&mut self, decl: &hir::Decl) -> io::Result<()> {
1544         self.maybe_print_comment(decl.span.lo())?;
1545         match decl.node {
1546             hir::DeclLocal(ref loc) => {
1547                 self.space_if_not_bol()?;
1548                 self.ibox(indent_unit)?;
1549                 self.word_nbsp("let")?;
1550
1551                 self.ibox(indent_unit)?;
1552                 self.print_local_decl(&loc)?;
1553                 self.end()?;
1554                 if let Some(ref init) = loc.init {
1555                     self.nbsp()?;
1556                     self.word_space("=")?;
1557                     self.print_expr(&init)?;
1558                 }
1559                 self.end()
1560             }
1561             hir::DeclItem(item) => {
1562                 self.ann.nested(self, Nested::Item(item))
1563             }
1564         }
1565     }
1566
1567     pub fn print_usize(&mut self, i: usize) -> io::Result<()> {
1568         self.s.word(&i.to_string())
1569     }
1570
1571     pub fn print_name(&mut self, name: ast::Name) -> io::Result<()> {
1572         self.s.word(&name.as_str())?;
1573         self.ann.post(self, NodeName(&name))
1574     }
1575
1576     pub fn print_for_decl(&mut self, loc: &hir::Local, coll: &hir::Expr) -> io::Result<()> {
1577         self.print_local_decl(loc)?;
1578         self.s.space()?;
1579         self.word_space("in")?;
1580         self.print_expr(coll)
1581     }
1582
1583     pub fn print_path(&mut self,
1584                       path: &hir::Path,
1585                       colons_before_params: bool)
1586                       -> io::Result<()> {
1587         self.maybe_print_comment(path.span.lo())?;
1588
1589         for (i, segment) in path.segments.iter().enumerate() {
1590             if i > 0 {
1591                 self.s.word("::")?
1592             }
1593             if segment.name != keywords::CrateRoot.name() &&
1594                segment.name != keywords::DollarCrate.name() {
1595                self.print_name(segment.name)?;
1596                segment.with_parameters(|parameters| {
1597                    self.print_path_parameters(parameters,
1598                                               segment.infer_types,
1599                                               colons_before_params)
1600                })?;
1601             }
1602         }
1603
1604         Ok(())
1605     }
1606
1607     pub fn print_qpath(&mut self,
1608                        qpath: &hir::QPath,
1609                        colons_before_params: bool)
1610                        -> io::Result<()> {
1611         match *qpath {
1612             hir::QPath::Resolved(None, ref path) => {
1613                 self.print_path(path, colons_before_params)
1614             }
1615             hir::QPath::Resolved(Some(ref qself), ref path) => {
1616                 self.s.word("<")?;
1617                 self.print_type(qself)?;
1618                 self.s.space()?;
1619                 self.word_space("as")?;
1620
1621                 for (i, segment) in path.segments[..path.segments.len() - 1].iter().enumerate() {
1622                     if i > 0 {
1623                         self.s.word("::")?
1624                     }
1625                     if segment.name != keywords::CrateRoot.name() &&
1626                        segment.name != keywords::DollarCrate.name() {
1627                         self.print_name(segment.name)?;
1628                         segment.with_parameters(|parameters| {
1629                             self.print_path_parameters(parameters,
1630                                                        segment.infer_types,
1631                                                        colons_before_params)
1632                         })?;
1633                     }
1634                 }
1635
1636                 self.s.word(">")?;
1637                 self.s.word("::")?;
1638                 let item_segment = path.segments.last().unwrap();
1639                 self.print_name(item_segment.name)?;
1640                 item_segment.with_parameters(|parameters| {
1641                     self.print_path_parameters(parameters,
1642                                                item_segment.infer_types,
1643                                                colons_before_params)
1644                 })
1645             }
1646             hir::QPath::TypeRelative(ref qself, ref item_segment) => {
1647                 self.s.word("<")?;
1648                 self.print_type(qself)?;
1649                 self.s.word(">")?;
1650                 self.s.word("::")?;
1651                 self.print_name(item_segment.name)?;
1652                 item_segment.with_parameters(|parameters| {
1653                     self.print_path_parameters(parameters,
1654                                                item_segment.infer_types,
1655                                                colons_before_params)
1656                 })
1657             }
1658         }
1659     }
1660
1661     fn print_path_parameters(&mut self,
1662                              parameters: &hir::PathParameters,
1663                              infer_types: bool,
1664                              colons_before_params: bool)
1665                              -> io::Result<()> {
1666         if parameters.parenthesized {
1667             self.s.word("(")?;
1668             self.commasep(Inconsistent, parameters.inputs(), |s, ty| s.print_type(&ty))?;
1669             self.s.word(")")?;
1670
1671             self.space_if_not_bol()?;
1672             self.word_space("->")?;
1673             self.print_type(&parameters.bindings[0].ty)?;
1674         } else {
1675             let start = if colons_before_params { "::<" } else { "<" };
1676             let empty = Cell::new(true);
1677             let start_or_comma = |this: &mut Self| {
1678                 if empty.get() {
1679                     empty.set(false);
1680                     this.s.word(start)
1681                 } else {
1682                     this.word_space(",")
1683                 }
1684             };
1685
1686             if !parameters.lifetimes.iter().all(|lt| lt.is_elided()) {
1687                 for lifetime in &parameters.lifetimes {
1688                     start_or_comma(self)?;
1689                     self.print_lifetime(lifetime)?;
1690                 }
1691             }
1692
1693             if !parameters.types.is_empty() {
1694                 start_or_comma(self)?;
1695                 self.commasep(Inconsistent, &parameters.types, |s, ty| s.print_type(&ty))?;
1696             }
1697
1698             // FIXME(eddyb) This would leak into error messages, e.g.:
1699             // "non-exhaustive patterns: `Some::<..>(_)` not covered".
1700             if infer_types && false {
1701                 start_or_comma(self)?;
1702                 self.s.word("..")?;
1703             }
1704
1705             for binding in parameters.bindings.iter() {
1706                 start_or_comma(self)?;
1707                 self.print_name(binding.name)?;
1708                 self.s.space()?;
1709                 self.word_space("=")?;
1710                 self.print_type(&binding.ty)?;
1711             }
1712
1713             if !empty.get() {
1714                 self.s.word(">")?
1715             }
1716         }
1717
1718         Ok(())
1719     }
1720
1721     pub fn print_pat(&mut self, pat: &hir::Pat) -> io::Result<()> {
1722         self.maybe_print_comment(pat.span.lo())?;
1723         self.ann.pre(self, NodePat(pat))?;
1724         // Pat isn't normalized, but the beauty of it
1725         // is that it doesn't matter
1726         match pat.node {
1727             PatKind::Wild => self.s.word("_")?,
1728             PatKind::Binding(binding_mode, _, ref path1, ref sub) => {
1729                 match binding_mode {
1730                     hir::BindingAnnotation::Ref => {
1731                         self.word_nbsp("ref")?;
1732                         self.print_mutability(hir::MutImmutable)?;
1733                     }
1734                     hir::BindingAnnotation::RefMut => {
1735                         self.word_nbsp("ref")?;
1736                         self.print_mutability(hir::MutMutable)?;
1737                     }
1738                     hir::BindingAnnotation::Unannotated => {}
1739                     hir::BindingAnnotation::Mutable => {
1740                         self.word_nbsp("mut")?;
1741                     }
1742                 }
1743                 self.print_name(path1.node)?;
1744                 if let Some(ref p) = *sub {
1745                     self.s.word("@")?;
1746                     self.print_pat(&p)?;
1747                 }
1748             }
1749             PatKind::TupleStruct(ref qpath, ref elts, ddpos) => {
1750                 self.print_qpath(qpath, true)?;
1751                 self.popen()?;
1752                 if let Some(ddpos) = ddpos {
1753                     self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(&p))?;
1754                     if ddpos != 0 {
1755                         self.word_space(",")?;
1756                     }
1757                     self.s.word("..")?;
1758                     if ddpos != elts.len() {
1759                         self.s.word(",")?;
1760                         self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(&p))?;
1761                     }
1762                 } else {
1763                     self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(&p))?;
1764                 }
1765                 self.pclose()?;
1766             }
1767             PatKind::Path(ref qpath) => {
1768                 self.print_qpath(qpath, true)?;
1769             }
1770             PatKind::Struct(ref qpath, ref fields, etc) => {
1771                 self.print_qpath(qpath, true)?;
1772                 self.nbsp()?;
1773                 self.word_space("{")?;
1774                 self.commasep_cmnt(Consistent,
1775                                    &fields[..],
1776                                    |s, f| {
1777                                        s.cbox(indent_unit)?;
1778                                        if !f.node.is_shorthand {
1779                                            s.print_name(f.node.name)?;
1780                                            s.word_nbsp(":")?;
1781                                        }
1782                                        s.print_pat(&f.node.pat)?;
1783                                        s.end()
1784                                    },
1785                                    |f| f.node.pat.span)?;
1786                 if etc {
1787                     if !fields.is_empty() {
1788                         self.word_space(",")?;
1789                     }
1790                     self.s.word("..")?;
1791                 }
1792                 self.s.space()?;
1793                 self.s.word("}")?;
1794             }
1795             PatKind::Tuple(ref elts, ddpos) => {
1796                 self.popen()?;
1797                 if let Some(ddpos) = ddpos {
1798                     self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(&p))?;
1799                     if ddpos != 0 {
1800                         self.word_space(",")?;
1801                     }
1802                     self.s.word("..")?;
1803                     if ddpos != elts.len() {
1804                         self.s.word(",")?;
1805                         self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(&p))?;
1806                     }
1807                 } else {
1808                     self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(&p))?;
1809                     if elts.len() == 1 {
1810                         self.s.word(",")?;
1811                     }
1812                 }
1813                 self.pclose()?;
1814             }
1815             PatKind::Box(ref inner) => {
1816                 self.s.word("box ")?;
1817                 self.print_pat(&inner)?;
1818             }
1819             PatKind::Ref(ref inner, mutbl) => {
1820                 self.s.word("&")?;
1821                 if mutbl == hir::MutMutable {
1822                     self.s.word("mut ")?;
1823                 }
1824                 self.print_pat(&inner)?;
1825             }
1826             PatKind::Lit(ref e) => self.print_expr(&e)?,
1827             PatKind::Range(ref begin, ref end, ref end_kind) => {
1828                 self.print_expr(&begin)?;
1829                 self.s.space()?;
1830                 match *end_kind {
1831                     RangeEnd::Included => self.s.word("...")?,
1832                     RangeEnd::Excluded => self.s.word("..")?,
1833                 }
1834                 self.print_expr(&end)?;
1835             }
1836             PatKind::Slice(ref before, ref slice, ref after) => {
1837                 self.s.word("[")?;
1838                 self.commasep(Inconsistent, &before[..], |s, p| s.print_pat(&p))?;
1839                 if let Some(ref p) = *slice {
1840                     if !before.is_empty() {
1841                         self.word_space(",")?;
1842                     }
1843                     if p.node != PatKind::Wild {
1844                         self.print_pat(&p)?;
1845                     }
1846                     self.s.word("..")?;
1847                     if !after.is_empty() {
1848                         self.word_space(",")?;
1849                     }
1850                 }
1851                 self.commasep(Inconsistent, &after[..], |s, p| s.print_pat(&p))?;
1852                 self.s.word("]")?;
1853             }
1854         }
1855         self.ann.post(self, NodePat(pat))
1856     }
1857
1858     fn print_arm(&mut self, arm: &hir::Arm) -> io::Result<()> {
1859         // I have no idea why this check is necessary, but here it
1860         // is :(
1861         if arm.attrs.is_empty() {
1862             self.s.space()?;
1863         }
1864         self.cbox(indent_unit)?;
1865         self.ibox(0)?;
1866         self.print_outer_attributes(&arm.attrs)?;
1867         let mut first = true;
1868         for p in &arm.pats {
1869             if first {
1870                 first = false;
1871             } else {
1872                 self.s.space()?;
1873                 self.word_space("|")?;
1874             }
1875             self.print_pat(&p)?;
1876         }
1877         self.s.space()?;
1878         if let Some(ref e) = arm.guard {
1879             self.word_space("if")?;
1880             self.print_expr(&e)?;
1881             self.s.space()?;
1882         }
1883         self.word_space("=>")?;
1884
1885         match arm.body.node {
1886             hir::ExprBlock(ref blk) => {
1887                 // the block will close the pattern's ibox
1888                 self.print_block_unclosed_indent(&blk, indent_unit)?;
1889
1890                 // If it is a user-provided unsafe block, print a comma after it
1891                 if let hir::UnsafeBlock(hir::UserProvided) = blk.rules {
1892                     self.s.word(",")?;
1893                 }
1894             }
1895             _ => {
1896                 self.end()?; // close the ibox for the pattern
1897                 self.print_expr(&arm.body)?;
1898                 self.s.word(",")?;
1899             }
1900         }
1901         self.end() // close enclosing cbox
1902     }
1903
1904     pub fn print_fn(&mut self,
1905                     decl: &hir::FnDecl,
1906                     unsafety: hir::Unsafety,
1907                     constness: hir::Constness,
1908                     abi: Abi,
1909                     name: Option<ast::Name>,
1910                     generics: &hir::Generics,
1911                     vis: &hir::Visibility,
1912                     arg_names: &[Spanned<ast::Name>],
1913                     body_id: Option<hir::BodyId>)
1914                     -> io::Result<()> {
1915         self.print_fn_header_info(unsafety, constness, abi, vis)?;
1916
1917         if let Some(name) = name {
1918             self.nbsp()?;
1919             self.print_name(name)?;
1920         }
1921         self.print_generics(generics)?;
1922
1923         self.popen()?;
1924         let mut i = 0;
1925         // Make sure we aren't supplied *both* `arg_names` and `body_id`.
1926         assert!(arg_names.is_empty() || body_id.is_none());
1927         self.commasep(Inconsistent, &decl.inputs, |s, ty| {
1928             s.ibox(indent_unit)?;
1929             if let Some(name) = arg_names.get(i) {
1930                 s.s.word(&name.node.as_str())?;
1931                 s.s.word(":")?;
1932                 s.s.space()?;
1933             } else if let Some(body_id) = body_id {
1934                 s.ann.nested(s, Nested::BodyArgPat(body_id, i))?;
1935                 s.s.word(":")?;
1936                 s.s.space()?;
1937             }
1938             i += 1;
1939             s.print_type(ty)?;
1940             s.end()
1941         })?;
1942         if decl.variadic {
1943             self.s.word(", ...")?;
1944         }
1945         self.pclose()?;
1946
1947         self.print_fn_output(decl)?;
1948         self.print_where_clause(&generics.where_clause)
1949     }
1950
1951     fn print_closure_args(&mut self, decl: &hir::FnDecl, body_id: hir::BodyId) -> io::Result<()> {
1952         self.s.word("|")?;
1953         let mut i = 0;
1954         self.commasep(Inconsistent, &decl.inputs, |s, ty| {
1955             s.ibox(indent_unit)?;
1956
1957             s.ann.nested(s, Nested::BodyArgPat(body_id, i))?;
1958             i += 1;
1959
1960             if ty.node != hir::TyInfer {
1961                 s.s.word(":")?;
1962                 s.s.space()?;
1963                 s.print_type(ty)?;
1964             }
1965             s.end()
1966         })?;
1967         self.s.word("|")?;
1968
1969         if let hir::DefaultReturn(..) = decl.output {
1970             return Ok(());
1971         }
1972
1973         self.space_if_not_bol()?;
1974         self.word_space("->")?;
1975         match decl.output {
1976             hir::Return(ref ty) => {
1977                 self.print_type(&ty)?;
1978                 self.maybe_print_comment(ty.span.lo())
1979             }
1980             hir::DefaultReturn(..) => unreachable!(),
1981         }
1982     }
1983
1984     pub fn print_capture_clause(&mut self, capture_clause: hir::CaptureClause) -> io::Result<()> {
1985         match capture_clause {
1986             hir::CaptureByValue => self.word_space("move"),
1987             hir::CaptureByRef => Ok(()),
1988         }
1989     }
1990
1991     pub fn print_bounds(&mut self, prefix: &str, bounds: &[hir::TyParamBound]) -> io::Result<()> {
1992         if !bounds.is_empty() {
1993             self.s.word(prefix)?;
1994             let mut first = true;
1995             for bound in bounds {
1996                 self.nbsp()?;
1997                 if first {
1998                     first = false;
1999                 } else {
2000                     self.word_space("+")?;
2001                 }
2002
2003                 match *bound {
2004                     TraitTyParamBound(ref tref, TraitBoundModifier::None) => {
2005                         self.print_poly_trait_ref(tref)
2006                     }
2007                     TraitTyParamBound(ref tref, TraitBoundModifier::Maybe) => {
2008                         self.s.word("?")?;
2009                         self.print_poly_trait_ref(tref)
2010                     }
2011                     RegionTyParamBound(ref lt) => {
2012                         self.print_lifetime(lt)
2013                     }
2014                 }?
2015             }
2016             Ok(())
2017         } else {
2018             Ok(())
2019         }
2020     }
2021
2022     pub fn print_lifetime(&mut self, lifetime: &hir::Lifetime) -> io::Result<()> {
2023         self.print_name(lifetime.name.name())
2024     }
2025
2026     pub fn print_lifetime_def(&mut self, lifetime: &hir::LifetimeDef) -> io::Result<()> {
2027         self.print_lifetime(&lifetime.lifetime)?;
2028         let mut sep = ":";
2029         for v in &lifetime.bounds {
2030             self.s.word(sep)?;
2031             self.print_lifetime(v)?;
2032             sep = "+";
2033         }
2034         Ok(())
2035     }
2036
2037     pub fn print_generics(&mut self, generics: &hir::Generics) -> io::Result<()> {
2038         let total = generics.lifetimes.len() + generics.ty_params.len();
2039         if total == 0 {
2040             return Ok(());
2041         }
2042
2043         self.s.word("<")?;
2044
2045         let mut ints = Vec::new();
2046         for i in 0..total {
2047             ints.push(i);
2048         }
2049
2050         self.commasep(Inconsistent, &ints[..], |s, &idx| {
2051             if idx < generics.lifetimes.len() {
2052                 let lifetime = &generics.lifetimes[idx];
2053                 s.print_lifetime_def(lifetime)
2054             } else {
2055                 let idx = idx - generics.lifetimes.len();
2056                 let param = &generics.ty_params[idx];
2057                 s.print_ty_param(param)
2058             }
2059         })?;
2060
2061         self.s.word(">")?;
2062         Ok(())
2063     }
2064
2065     pub fn print_ty_param(&mut self, param: &hir::TyParam) -> io::Result<()> {
2066         self.print_name(param.name)?;
2067         self.print_bounds(":", &param.bounds)?;
2068         match param.default {
2069             Some(ref default) => {
2070                 self.s.space()?;
2071                 self.word_space("=")?;
2072                 self.print_type(&default)
2073             }
2074             _ => Ok(()),
2075         }
2076     }
2077
2078     pub fn print_where_clause(&mut self, where_clause: &hir::WhereClause) -> io::Result<()> {
2079         if where_clause.predicates.is_empty() {
2080             return Ok(());
2081         }
2082
2083         self.s.space()?;
2084         self.word_space("where")?;
2085
2086         for (i, predicate) in where_clause.predicates.iter().enumerate() {
2087             if i != 0 {
2088                 self.word_space(",")?;
2089             }
2090
2091             match predicate {
2092                 &hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate{ref bound_lifetimes,
2093                                                                               ref bounded_ty,
2094                                                                               ref bounds,
2095                                                                               ..}) => {
2096                     self.print_formal_lifetime_list(bound_lifetimes)?;
2097                     self.print_type(&bounded_ty)?;
2098                     self.print_bounds(":", bounds)?;
2099                 }
2100                 &hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate{ref lifetime,
2101                                                                                 ref bounds,
2102                                                                                 ..}) => {
2103                     self.print_lifetime(lifetime)?;
2104                     self.s.word(":")?;
2105
2106                     for (i, bound) in bounds.iter().enumerate() {
2107                         self.print_lifetime(bound)?;
2108
2109                         if i != 0 {
2110                             self.s.word(":")?;
2111                         }
2112                     }
2113                 }
2114                 &hir::WherePredicate::EqPredicate(hir::WhereEqPredicate{ref lhs_ty,
2115                                                                         ref rhs_ty,
2116                                                                         ..}) => {
2117                     self.print_type(lhs_ty)?;
2118                     self.s.space()?;
2119                     self.word_space("=")?;
2120                     self.print_type(rhs_ty)?;
2121                 }
2122             }
2123         }
2124
2125         Ok(())
2126     }
2127
2128     pub fn print_mutability(&mut self, mutbl: hir::Mutability) -> io::Result<()> {
2129         match mutbl {
2130             hir::MutMutable => self.word_nbsp("mut"),
2131             hir::MutImmutable => Ok(()),
2132         }
2133     }
2134
2135     pub fn print_mt(&mut self, mt: &hir::MutTy) -> io::Result<()> {
2136         self.print_mutability(mt.mutbl)?;
2137         self.print_type(&mt.ty)
2138     }
2139
2140     pub fn print_fn_output(&mut self, decl: &hir::FnDecl) -> io::Result<()> {
2141         if let hir::DefaultReturn(..) = decl.output {
2142             return Ok(());
2143         }
2144
2145         self.space_if_not_bol()?;
2146         self.ibox(indent_unit)?;
2147         self.word_space("->")?;
2148         match decl.output {
2149             hir::DefaultReturn(..) => unreachable!(),
2150             hir::Return(ref ty) => self.print_type(&ty)?,
2151         }
2152         self.end()?;
2153
2154         match decl.output {
2155             hir::Return(ref output) => self.maybe_print_comment(output.span.lo()),
2156             _ => Ok(()),
2157         }
2158     }
2159
2160     pub fn print_ty_fn(&mut self,
2161                        abi: Abi,
2162                        unsafety: hir::Unsafety,
2163                        decl: &hir::FnDecl,
2164                        name: Option<ast::Name>,
2165                        generics: &hir::Generics,
2166                        arg_names: &[Spanned<ast::Name>])
2167                        -> io::Result<()> {
2168         self.ibox(indent_unit)?;
2169         if !generics.lifetimes.is_empty() || !generics.ty_params.is_empty() {
2170             self.s.word("for")?;
2171             self.print_generics(generics)?;
2172         }
2173         let generics = hir::Generics {
2174             lifetimes: hir::HirVec::new(),
2175             ty_params: hir::HirVec::new(),
2176             where_clause: hir::WhereClause {
2177                 id: ast::DUMMY_NODE_ID,
2178                 predicates: hir::HirVec::new(),
2179             },
2180             span: syntax_pos::DUMMY_SP,
2181         };
2182         self.print_fn(decl,
2183                       unsafety,
2184                       hir::Constness::NotConst,
2185                       abi,
2186                       name,
2187                       &generics,
2188                       &hir::Inherited,
2189                       arg_names,
2190                       None)?;
2191         self.end()
2192     }
2193
2194     pub fn maybe_print_trailing_comment(&mut self,
2195                                         span: syntax_pos::Span,
2196                                         next_pos: Option<BytePos>)
2197                                         -> io::Result<()> {
2198         let cm = match self.cm {
2199             Some(cm) => cm,
2200             _ => return Ok(()),
2201         };
2202         if let Some(ref cmnt) = self.next_comment() {
2203             if (*cmnt).style != comments::Trailing {
2204                 return Ok(());
2205             }
2206             let span_line = cm.lookup_char_pos(span.hi());
2207             let comment_line = cm.lookup_char_pos((*cmnt).pos);
2208             let mut next = (*cmnt).pos + BytePos(1);
2209             if let Some(p) = next_pos {
2210                 next = p;
2211             }
2212             if span.hi() < (*cmnt).pos && (*cmnt).pos < next &&
2213                span_line.line == comment_line.line {
2214                 self.print_comment(cmnt)?;
2215             }
2216         }
2217         Ok(())
2218     }
2219
2220     pub fn print_remaining_comments(&mut self) -> io::Result<()> {
2221         // If there aren't any remaining comments, then we need to manually
2222         // make sure there is a line break at the end.
2223         if self.next_comment().is_none() {
2224             self.s.hardbreak()?;
2225         }
2226         loop {
2227             match self.next_comment() {
2228                 Some(ref cmnt) => {
2229                     self.print_comment(cmnt)?;
2230                 }
2231                 _ => break,
2232             }
2233         }
2234         Ok(())
2235     }
2236
2237     pub fn print_opt_abi_and_extern_if_nondefault(&mut self,
2238                                                   opt_abi: Option<Abi>)
2239                                                   -> io::Result<()> {
2240         match opt_abi {
2241             Some(Abi::Rust) => Ok(()),
2242             Some(abi) => {
2243                 self.word_nbsp("extern")?;
2244                 self.word_nbsp(&abi.to_string())
2245             }
2246             None => Ok(()),
2247         }
2248     }
2249
2250     pub fn print_extern_opt_abi(&mut self, opt_abi: Option<Abi>) -> io::Result<()> {
2251         match opt_abi {
2252             Some(abi) => {
2253                 self.word_nbsp("extern")?;
2254                 self.word_nbsp(&abi.to_string())
2255             }
2256             None => Ok(()),
2257         }
2258     }
2259
2260     pub fn print_fn_header_info(&mut self,
2261                                 unsafety: hir::Unsafety,
2262                                 constness: hir::Constness,
2263                                 abi: Abi,
2264                                 vis: &hir::Visibility)
2265                                 -> io::Result<()> {
2266         self.s.word(&visibility_qualified(vis, ""))?;
2267         self.print_unsafety(unsafety)?;
2268
2269         match constness {
2270             hir::Constness::NotConst => {}
2271             hir::Constness::Const => self.word_nbsp("const")?,
2272         }
2273
2274         if abi != Abi::Rust {
2275             self.word_nbsp("extern")?;
2276             self.word_nbsp(&abi.to_string())?;
2277         }
2278
2279         self.s.word("fn")
2280     }
2281
2282     pub fn print_unsafety(&mut self, s: hir::Unsafety) -> io::Result<()> {
2283         match s {
2284             hir::Unsafety::Normal => Ok(()),
2285             hir::Unsafety::Unsafe => self.word_nbsp("unsafe"),
2286         }
2287     }
2288
2289     pub fn print_is_auto(&mut self, s: hir::IsAuto) -> io::Result<()> {
2290         match s {
2291             hir::IsAuto::Yes => self.word_nbsp("auto"),
2292             hir::IsAuto::No => Ok(()),
2293         }
2294     }
2295 }
2296
2297 // Dup'ed from parse::classify, but adapted for the HIR.
2298 /// Does this expression require a semicolon to be treated
2299 /// as a statement? The negation of this: 'can this expression
2300 /// be used as a statement without a semicolon' -- is used
2301 /// as an early-bail-out in the parser so that, for instance,
2302 ///     if true {...} else {...}
2303 ///      |x| 5
2304 /// isn't parsed as (if true {...} else {...} | x) | 5
2305 fn expr_requires_semi_to_be_stmt(e: &hir::Expr) -> bool {
2306     match e.node {
2307         hir::ExprIf(..) |
2308         hir::ExprMatch(..) |
2309         hir::ExprBlock(_) |
2310         hir::ExprWhile(..) |
2311         hir::ExprLoop(..) => false,
2312         _ => true,
2313     }
2314 }
2315
2316 /// this statement requires a semicolon after it.
2317 /// note that in one case (stmt_semi), we've already
2318 /// seen the semicolon, and thus don't need another.
2319 fn stmt_ends_with_semi(stmt: &hir::Stmt_) -> bool {
2320     match *stmt {
2321         hir::StmtDecl(ref d, _) => {
2322             match d.node {
2323                 hir::DeclLocal(_) => true,
2324                 hir::DeclItem(_) => false,
2325             }
2326         }
2327         hir::StmtExpr(ref e, _) => {
2328             expr_requires_semi_to_be_stmt(&e)
2329         }
2330         hir::StmtSemi(..) => {
2331             false
2332         }
2333     }
2334 }
2335
2336
2337 fn expr_precedence(expr: &hir::Expr) -> i8 {
2338     use syntax::util::parser::*;
2339
2340     match expr.node {
2341         hir::ExprClosure(..) => PREC_CLOSURE,
2342
2343         hir::ExprBreak(..) |
2344         hir::ExprAgain(..) |
2345         hir::ExprRet(..) |
2346         hir::ExprYield(..) => PREC_JUMP,
2347
2348         // Binop-like expr kinds, handled by `AssocOp`.
2349         hir::ExprBinary(op, _, _) => bin_op_to_assoc_op(op.node).precedence() as i8,
2350
2351         hir::ExprCast(..) => AssocOp::As.precedence() as i8,
2352         hir::ExprType(..) => AssocOp::Colon.precedence() as i8,
2353
2354         hir::ExprAssign(..) |
2355         hir::ExprAssignOp(..) => AssocOp::Assign.precedence() as i8,
2356
2357         // Unary, prefix
2358         hir::ExprBox(..) |
2359         hir::ExprAddrOf(..) |
2360         hir::ExprUnary(..) => PREC_PREFIX,
2361
2362         // Unary, postfix
2363         hir::ExprCall(..) |
2364         hir::ExprMethodCall(..) |
2365         hir::ExprField(..) |
2366         hir::ExprTupField(..) |
2367         hir::ExprIndex(..) |
2368         hir::ExprInlineAsm(..) => PREC_POSTFIX,
2369
2370         // Never need parens
2371         hir::ExprArray(..) |
2372         hir::ExprRepeat(..) |
2373         hir::ExprTup(..) |
2374         hir::ExprLit(..) |
2375         hir::ExprPath(..) |
2376         hir::ExprIf(..) |
2377         hir::ExprWhile(..) |
2378         hir::ExprLoop(..) |
2379         hir::ExprMatch(..) |
2380         hir::ExprBlock(..) |
2381         hir::ExprStruct(..) => PREC_PAREN,
2382     }
2383 }
2384
2385 fn bin_op_to_assoc_op(op: hir::BinOp_) -> AssocOp {
2386     use hir::BinOp_::*;
2387     match op {
2388         BiAdd => AssocOp::Add,
2389         BiSub => AssocOp::Subtract,
2390         BiMul => AssocOp::Multiply,
2391         BiDiv => AssocOp::Divide,
2392         BiRem => AssocOp::Modulus,
2393
2394         BiAnd => AssocOp::LAnd,
2395         BiOr => AssocOp::LOr,
2396
2397         BiBitXor => AssocOp::BitXor,
2398         BiBitAnd => AssocOp::BitAnd,
2399         BiBitOr => AssocOp::BitOr,
2400         BiShl => AssocOp::ShiftLeft,
2401         BiShr => AssocOp::ShiftRight,
2402
2403         BiEq => AssocOp::Equal,
2404         BiLt => AssocOp::Less,
2405         BiLe => AssocOp::LessEqual,
2406         BiNe => AssocOp::NotEqual,
2407         BiGe => AssocOp::GreaterEqual,
2408         BiGt => AssocOp::Greater,
2409     }
2410 }
2411
2412 /// Expressions that syntactically contain an "exterior" struct literal i.e. not surrounded by any
2413 /// parens or other delimiters, e.g. `X { y: 1 }`, `X { y: 1 }.method()`, `foo == X { y: 1 }` and
2414 /// `X { y: 1 } == foo` all do, but `(X { y: 1 }) == foo` does not.
2415 fn contains_exterior_struct_lit(value: &hir::Expr) -> bool {
2416     match value.node {
2417         hir::ExprStruct(..) => true,
2418
2419         hir::ExprAssign(ref lhs, ref rhs) |
2420         hir::ExprAssignOp(_, ref lhs, ref rhs) |
2421         hir::ExprBinary(_, ref lhs, ref rhs) => {
2422             // X { y: 1 } + X { y: 2 }
2423             contains_exterior_struct_lit(&lhs) || contains_exterior_struct_lit(&rhs)
2424         }
2425         hir::ExprUnary(_, ref x) |
2426         hir::ExprCast(ref x, _) |
2427         hir::ExprType(ref x, _) |
2428         hir::ExprField(ref x, _) |
2429         hir::ExprTupField(ref x, _) |
2430         hir::ExprIndex(ref x, _) => {
2431             // &X { y: 1 }, X { y: 1 }.y
2432             contains_exterior_struct_lit(&x)
2433         }
2434
2435         hir::ExprMethodCall(.., ref exprs) => {
2436             // X { y: 1 }.bar(...)
2437             contains_exterior_struct_lit(&exprs[0])
2438         }
2439
2440         _ => false,
2441     }
2442 }