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