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