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 use rustc_target::spec::abi::Abi;
  12 use syntax::ast;
  13 use syntax::source_map::{SourceMap, Spanned};
  14 use syntax::parse::ParseSess;
  15 use syntax::parse::lexer::comments;
  16 use syntax::print::pp::{self, Breaks};
  17 use syntax::print::pp::Breaks::{Consistent, Inconsistent};
  18 use syntax::print::pprust::PrintState;
  19 use syntax::ptr::P;
  20 use syntax::symbol::keywords;
  21 use syntax::util::parser::{self, AssocOp, Fixity};
  22 use syntax_pos::{self, BytePos, FileName};
  23
  24 use hir;
  25 use hir::{PatKind, GenericBound, TraitBoundModifier, RangeEnd};
  26 use hir::{GenericParam, GenericParamKind, GenericArg};
  27
  28 use std::cell::Cell;
  29 use std::io::{self, Write, Read};
  30 use std::iter::Peekable;
  31 use std::vec;
  32
  33 pub enum AnnNode<'a> {
  34     Name(&'a ast::Name),
  35     Block(&'a hir::Block),
  36     Item(&'a hir::Item),
  37     SubItem(ast::NodeId),
  38     Expr(&'a hir::Expr),
  39     Pat(&'a hir::Pat),
  40 }
  41
  42 pub enum Nested {
  43     Item(hir::ItemId),
  44     TraitItem(hir::TraitItemId),
  45     ImplItem(hir::ImplItemId),
  46     Body(hir::BodyId),
  47     BodyArgPat(hir::BodyId, usize)
  48 }
  49
  50 pub trait PpAnn {
  51     fn nested(&self, _state: &mut State, _nested: Nested) -> io::Result<()> {
  52         Ok(())
  53     }
  54     fn pre(&self, _state: &mut State, _node: AnnNode) -> io::Result<()> {
  55         Ok(())
  56     }
  57     fn post(&self, _state: &mut State, _node: AnnNode) -> io::Result<()> {
  58         Ok(())
  59     }
  60     fn try_fetch_item(&self, _: ast::NodeId) -> Option<&hir::Item> {
  61         None
  62     }
  63 }
  64
  65 pub struct NoAnn;
  66 impl PpAnn for NoAnn {}
  67 pub const NO_ANN: &'static dyn PpAnn = &NoAnn;
  68
  69 impl PpAnn for hir::Crate {
  70     fn try_fetch_item(&self, item: ast::NodeId) -> Option<&hir::Item> {
  71         Some(self.item(item))
  72     }
  73     fn nested(&self, state: &mut State, nested: Nested) -> io::Result<()> {
  74         match nested {
  75             Nested::Item(id) => state.print_item(self.item(id.id)),
  76             Nested::TraitItem(id) => state.print_trait_item(self.trait_item(id)),
  77             Nested::ImplItem(id) => state.print_impl_item(self.impl_item(id)),
  78             Nested::Body(id) => state.print_expr(&self.body(id).value),
  79             Nested::BodyArgPat(id, i) => state.print_pat(&self.body(id).arguments[i].pat)
  80         }
  81     }
  82 }
  83
  84 pub struct State<'a> {
  85     pub s: pp::Printer<'a>,
  86     cm: Option<&'a SourceMap>,
  87     comments: Option<Vec<comments::Comment>>,
  88     literals: Peekable<vec::IntoIter<comments::Literal>>,
  89     cur_cmnt: usize,
  90     boxes: Vec<pp::Breaks>,
  91     ann: &'a (dyn PpAnn + 'a),
  92 }
  93
  94 impl<'a> PrintState<'a> for State<'a> {
  95     fn writer(&mut self) -> &mut pp::Printer<'a> {
  96         &mut self.s
  97     }
  98
  99     fn boxes(&mut self) -> &mut Vec<pp::Breaks> {
 100         &mut self.boxes
 101     }
 102
 103     fn comments(&mut self) -> &mut Option<Vec<comments::Comment>> {
 104         &mut self.comments
 105     }
 106
 107     fn cur_cmnt(&mut self) -> &mut usize {
 108         &mut self.cur_cmnt
 109     }
 110
 111     fn cur_lit(&mut self) -> Option<&comments::Literal> {
 112         self.literals.peek()
 113     }
 114
 115     fn bump_lit(&mut self) -> Option<comments::Literal> {
 116         self.literals.next()
 117     }
 118 }
 119
 120 #[allow(non_upper_case_globals)]
 121 pub const indent_unit: usize = 4;
 122
 123 #[allow(non_upper_case_globals)]
 124 pub const default_columns: usize = 78;
 125
 126
 127 /// Requires you to pass an input filename and reader so that
 128 /// it can scan the input text for comments and literals to
 129 /// copy forward.
 130 pub fn print_crate<'a>(cm: &'a SourceMap,
 131                        sess: &ParseSess,
 132                        krate: &hir::Crate,
 133                        filename: FileName,
 134                        input: &mut dyn Read,
 135                        out: Box<dyn Write + 'a>,
 136                        ann: &'a dyn PpAnn,
 137                        is_expanded: bool)
 138                        -> io::Result<()> {
 139     let mut s = State::new_from_input(cm, sess, filename, input, out, ann, is_expanded);
 140
 141     // When printing the AST, we sometimes need to inject `#[no_std]` here.
 142     // Since you can't compile the HIR, it's not necessary.
 143
 144     s.print_mod(&krate.module, &krate.attrs)?;
 145     s.print_remaining_comments()?;
 146     s.s.eof()
 147 }
 148
 149 impl<'a> State<'a> {
 150     pub fn new_from_input(cm: &'a SourceMap,
 151                           sess: &ParseSess,
 152                           filename: FileName,
 153                           input: &mut dyn Read,
 154                           out: Box<dyn Write + 'a>,
 155                           ann: &'a dyn PpAnn,
 156                           is_expanded: bool)
 157                           -> State<'a> {
 158         let (cmnts, lits) = comments::gather_comments_and_literals(sess, filename, input);
 159
 160         State::new(cm,
 161                    out,
 162                    ann,
 163                    Some(cmnts),
 164                    // If the code is post expansion, don't use the table of
 165                    // literals, since it doesn't correspond with the literals
 166                    // in the AST anymore.
 167                    if is_expanded {
 168                        None
 169                    } else {
 170                        Some(lits)
 171                    })
 172     }
 173
 174     pub fn new(cm: &'a SourceMap,
 175                out: Box<dyn Write + 'a>,
 176                ann: &'a dyn PpAnn,
 177                comments: Option<Vec<comments::Comment>>,
 178                literals: Option<Vec<comments::Literal>>)
 179                -> State<'a> {
 180         State {
 181             s: pp::mk_printer(out, default_columns),
 182             cm: Some(cm),
 183             comments: comments.clone(),
 184             literals: literals.unwrap_or_default().into_iter().peekable(),
 185             cur_cmnt: 0,
 186             boxes: Vec::new(),
 187             ann,
 188         }
 189     }
 190 }
 191
 192 pub fn to_string<F>(ann: &dyn PpAnn, f: F) -> String
 193     where F: FnOnce(&mut State) -> io::Result<()>
 194 {
 195     let mut wr = Vec::new();
 196     {
 197         let mut printer = State {
 198             s: pp::mk_printer(Box::new(&mut wr), default_columns),
 199             cm: None,
 200             comments: None,
 201             literals: vec![].into_iter().peekable(),
 202             cur_cmnt: 0,
 203             boxes: Vec::new(),
 204             ann,
 205         };
 206         f(&mut printer).unwrap();
 207         printer.s.eof().unwrap();
 208     }
 209     String::from_utf8(wr).unwrap()
 210 }
 211
 212 pub fn visibility_qualified(vis: &hir::Visibility, w: &str) -> String {
 213     to_string(NO_ANN, |s| {
 214         s.print_visibility(vis)?;
 215         s.s.word(w)
 216     })
 217 }
 218
 219 impl<'a> State<'a> {
 220     pub fn cbox(&mut self, u: usize) -> io::Result<()> {
 221         self.boxes.push(pp::Breaks::Consistent);
 222         self.s.cbox(u)
 223     }
 224
 225     pub fn nbsp(&mut self) -> io::Result<()> {
 226         self.s.word(" ")
 227     }
 228
 229     pub fn word_nbsp(&mut self, w: &str) -> io::Result<()> {
 230         self.s.word(w)?;
 231         self.nbsp()
 232     }
 233
 234     pub fn head(&mut self, w: &str) -> io::Result<()> {
 235         // outer-box is consistent
 236         self.cbox(indent_unit)?;
 237         // head-box is inconsistent
 238         self.ibox(w.len() + 1)?;
 239         // keyword that starts the head
 240         if !w.is_empty() {
 241             self.word_nbsp(w)?;
 242         }
 243         Ok(())
 244     }
 245
 246     pub fn bopen(&mut self) -> io::Result<()> {
 247         self.s.word("{")?;
 248         self.end() // close the head-box
 249     }
 250
 251     pub fn bclose_(&mut self, span: syntax_pos::Span, indented: usize) -> io::Result<()> {
 252         self.bclose_maybe_open(span, indented, true)
 253     }
 254
 255     pub fn bclose_maybe_open(&mut self,
 256                              span: syntax_pos::Span,
 257                              indented: usize,
 258                              close_box: bool)
 259                              -> io::Result<()> {
 260         self.maybe_print_comment(span.hi())?;
 261         self.break_offset_if_not_bol(1, -(indented as isize))?;
 262         self.s.word("}")?;
 263         if close_box {
 264             self.end()?; // close the outer-box
 265         }
 266         Ok(())
 267     }
 268
 269     pub fn bclose(&mut self, span: syntax_pos::Span) -> io::Result<()> {
 270         self.bclose_(span, indent_unit)
 271     }
 272
 273     pub fn in_cbox(&self) -> bool {
 274         match self.boxes.last() {
 275             Some(&last_box) => last_box == pp::Breaks::Consistent,
 276             None => false,
 277         }
 278     }
 279
 280     pub fn space_if_not_bol(&mut self) -> io::Result<()> {
 281         if !self.is_bol() {
 282             self.s.space()?;
 283         }
 284         Ok(())
 285     }
 286
 287     pub fn break_offset_if_not_bol(&mut self, n: usize, off: isize) -> io::Result<()> {
 288         if !self.is_bol() {
 289             self.s.break_offset(n, off)
 290         } else {
 291             if off != 0 && self.s.last_token().is_hardbreak_tok() {
 292                 // We do something pretty sketchy here: tuck the nonzero
 293                 // offset-adjustment we were going to deposit along with the
 294                 // break into the previous hardbreak.
 295                 self.s.replace_last_token(pp::Printer::hardbreak_tok_offset(off));
 296             }
 297             Ok(())
 298         }
 299     }
 300
 301     // Synthesizes a comment that was not textually present in the original source
 302     // file.
 303     pub fn synth_comment(&mut self, text: String) -> io::Result<()> {
 304         self.s.word("/*")?;
 305         self.s.space()?;
 306         self.s.word(&text[..])?;
 307         self.s.space()?;
 308         self.s.word("*/")
 309     }
 310
 311     pub fn commasep_cmnt<T, F, G>(&mut self,
 312                                   b: Breaks,
 313                                   elts: &[T],
 314                                   mut op: F,
 315                                   mut get_span: G)
 316                                   -> io::Result<()>
 317         where F: FnMut(&mut State, &T) -> io::Result<()>,
 318               G: FnMut(&T) -> syntax_pos::Span
 319     {
 320         self.rbox(0, b)?;
 321         let len = elts.len();
 322         let mut i = 0;
 323         for elt in elts {
 324             self.maybe_print_comment(get_span(elt).hi())?;
 325             op(self, elt)?;
 326             i += 1;
 327             if i < len {
 328                 self.s.word(",")?;
 329                 self.maybe_print_trailing_comment(get_span(elt), Some(get_span(&elts[i]).hi()))?;
 330                 self.space_if_not_bol()?;
 331             }
 332         }
 333         self.end()
 334     }
 335
 336     pub fn commasep_exprs(&mut self, b: Breaks, exprs: &[hir::Expr]) -> io::Result<()> {
 337         self.commasep_cmnt(b, exprs, |s, e| s.print_expr(&e), |e| e.span)
 338     }
 339
 340     pub fn print_mod(&mut self, _mod: &hir::Mod, attrs: &[ast::Attribute]) -> io::Result<()> {
 341         self.print_inner_attributes(attrs)?;
 342         for &item_id in &_mod.item_ids {
 343             self.ann.nested(self, Nested::Item(item_id))?;
 344         }
 345         Ok(())
 346     }
 347
 348     pub fn print_foreign_mod(&mut self,
 349                              nmod: &hir::ForeignMod,
 350                              attrs: &[ast::Attribute])
 351                              -> io::Result<()> {
 352         self.print_inner_attributes(attrs)?;
 353         for item in &nmod.items {
 354             self.print_foreign_item(item)?;
 355         }
 356         Ok(())
 357     }
 358
 359     pub fn print_opt_lifetime(&mut self, lifetime: &hir::Lifetime) -> io::Result<()> {
 360         if !lifetime.is_elided() {
 361             self.print_lifetime(lifetime)?;
 362             self.nbsp()?;
 363         }
 364         Ok(())
 365     }
 366
 367     pub fn print_type(&mut self, ty: &hir::Ty) -> io::Result<()> {
 368         self.maybe_print_comment(ty.span.lo())?;
 369         self.ibox(0)?;
 370         match ty.node {
 371             hir::TyKind::Slice(ref ty) => {
 372                 self.s.word("[")?;
 373                 self.print_type(&ty)?;
 374                 self.s.word("]")?;
 375             }
 376             hir::TyKind::Ptr(ref mt) => {
 377                 self.s.word("*")?;
 378                 match mt.mutbl {
 379                     hir::MutMutable => self.word_nbsp("mut")?,
 380                     hir::MutImmutable => self.word_nbsp("const")?,
 381                 }
 382                 self.print_type(&mt.ty)?;
 383             }
 384             hir::TyKind::Rptr(ref lifetime, ref mt) => {
 385                 self.s.word("&")?;
 386                 self.print_opt_lifetime(lifetime)?;
 387                 self.print_mt(mt)?;
 388             }
 389             hir::TyKind::Never => {
 390                 self.s.word("!")?;
 391             },
 392             hir::TyKind::Tup(ref elts) => {
 393                 self.popen()?;
 394                 self.commasep(Inconsistent, &elts[..], |s, ty| s.print_type(&ty))?;
 395                 if elts.len() == 1 {
 396                     self.s.word(",")?;
 397                 }
 398                 self.pclose()?;
 399             }
 400             hir::TyKind::BareFn(ref f) => {
 401                 self.print_ty_fn(f.abi, f.unsafety, &f.decl, None, &f.generic_params,
 402                                  &f.arg_names[..])?;
 403             }
 404             hir::TyKind::Path(ref qpath) => {
 405                 self.print_qpath(qpath, false)?
 406             }
 407             hir::TyKind::TraitObject(ref bounds, ref lifetime) => {
 408                 let mut first = true;
 409                 for bound in bounds {
 410                     if first {
 411                         first = false;
 412                     } else {
 413                         self.nbsp()?;
 414                         self.word_space("+")?;
 415                     }
 416                     self.print_poly_trait_ref(bound)?;
 417                 }
 418                 if !lifetime.is_elided() {
 419                     self.nbsp()?;
 420                     self.word_space("+")?;
 421                     self.print_lifetime(lifetime)?;
 422                 }
 423             }
 424             hir::TyKind::Array(ref ty, ref length) => {
 425                 self.s.word("[")?;
 426                 self.print_type(&ty)?;
 427                 self.s.word("; ")?;
 428                 self.print_anon_const(length)?;
 429                 self.s.word("]")?;
 430             }
 431             hir::TyKind::Typeof(ref e) => {
 432                 self.s.word("typeof(")?;
 433                 self.print_anon_const(e)?;
 434                 self.s.word(")")?;
 435             }
 436             hir::TyKind::Infer => {
 437                 self.s.word("_")?;
 438             }
 439             hir::TyKind::Err => {
 440                 self.s.word("?")?;
 441             }
 442         }
 443         self.end()
 444     }
 445
 446     pub fn print_foreign_item(&mut self, item: &hir::ForeignItem) -> io::Result<()> {
 447         self.hardbreak_if_not_bol()?;
 448         self.maybe_print_comment(item.span.lo())?;
 449         self.print_outer_attributes(&item.attrs)?;
 450         match item.node {
 451             hir::ForeignItemKind::Fn(ref decl, ref arg_names, ref generics) => {
 452                 self.head("")?;
 453                 self.print_fn(decl,
 454                               hir::FnHeader {
 455                                   unsafety: hir::Unsafety::Normal,
 456                                   constness: hir::Constness::NotConst,
 457                                   abi: Abi::Rust,
 458                                   asyncness: hir::IsAsync::NotAsync,
 459                               },
 460                               Some(item.name),
 461                               generics,
 462                               &item.vis,
 463                               arg_names,
 464                               None)?;
 465                 self.end()?; // end head-ibox
 466                 self.s.word(";")?;
 467                 self.end() // end the outer fn box
 468             }
 469             hir::ForeignItemKind::Static(ref t, m) => {
 470                 self.head(&visibility_qualified(&item.vis, "static"))?;
 471                 if m {
 472                     self.word_space("mut")?;
 473                 }
 474                 self.print_name(item.name)?;
 475                 self.word_space(":")?;
 476                 self.print_type(&t)?;
 477                 self.s.word(";")?;
 478                 self.end()?; // end the head-ibox
 479                 self.end() // end the outer cbox
 480             }
 481             hir::ForeignItemKind::Type => {
 482                 self.head(&visibility_qualified(&item.vis, "type"))?;
 483                 self.print_name(item.name)?;
 484                 self.s.word(";")?;
 485                 self.end()?; // end the head-ibox
 486                 self.end() // end the outer cbox
 487             }
 488         }
 489     }
 490
 491     fn print_associated_const(&mut self,
 492                               ident: ast::Ident,
 493                               ty: &hir::Ty,
 494                               default: Option<hir::BodyId>,
 495                               vis: &hir::Visibility)
 496                               -> io::Result<()> {
 497         self.s.word(&visibility_qualified(vis, ""))?;
 498         self.word_space("const")?;
 499         self.print_ident(ident)?;
 500         self.word_space(":")?;
 501         self.print_type(ty)?;
 502         if let Some(expr) = default {
 503             self.s.space()?;
 504             self.word_space("=")?;
 505             self.ann.nested(self, Nested::Body(expr))?;
 506         }
 507         self.s.word(";")
 508     }
 509
 510     fn print_associated_type(&mut self,
 511                              ident: ast::Ident,
 512                              bounds: Option<&hir::GenericBounds>,
 513                              ty: Option<&hir::Ty>)
 514                              -> io::Result<()> {
 515         self.word_space("type")?;
 516         self.print_ident(ident)?;
 517         if let Some(bounds) = bounds {
 518             self.print_bounds(":", bounds)?;
 519         }
 520         if let Some(ty) = ty {
 521             self.s.space()?;
 522             self.word_space("=")?;
 523             self.print_type(ty)?;
 524         }
 525         self.s.word(";")
 526     }
 527
 528     /// Pretty-print an item
 529     pub fn print_item(&mut self, item: &hir::Item) -> io::Result<()> {
 530         self.hardbreak_if_not_bol()?;
 531         self.maybe_print_comment(item.span.lo())?;
 532         self.print_outer_attributes(&item.attrs)?;
 533         self.ann.pre(self, AnnNode::Item(item))?;
 534         match item.node {
 535             hir::ItemKind::ExternCrate(orig_name) => {
 536                 self.head(&visibility_qualified(&item.vis, "extern crate"))?;
 537                 if let Some(orig_name) = orig_name {
 538                     self.print_name(orig_name)?;
 539                     self.s.space()?;
 540                     self.s.word("as")?;
 541                     self.s.space()?;
 542                 }
 543                 self.print_name(item.name)?;
 544                 self.s.word(";")?;
 545                 self.end()?; // end inner head-block
 546                 self.end()?; // end outer head-block
 547             }
 548             hir::ItemKind::Use(ref path, kind) => {
 549                 self.head(&visibility_qualified(&item.vis, "use"))?;
 550                 self.print_path(path, false)?;
 551
 552                 match kind {
 553                     hir::UseKind::Single => {
 554                         if path.segments.last().unwrap().ident.name != item.name {
 555                             self.s.space()?;
 556                             self.word_space("as")?;
 557                             self.print_name(item.name)?;
 558                         }
 559                         self.s.word(";")?;
 560                     }
 561                     hir::UseKind::Glob => self.s.word("::*;")?,
 562                     hir::UseKind::ListStem => self.s.word("::{};")?
 563                 }
 564                 self.end()?; // end inner head-block
 565                 self.end()?; // end outer head-block
 566             }
 567             hir::ItemKind::Static(ref ty, m, expr) => {
 568                 self.head(&visibility_qualified(&item.vis, "static"))?;
 569                 if m == hir::MutMutable {
 570                     self.word_space("mut")?;
 571                 }
 572                 self.print_name(item.name)?;
 573                 self.word_space(":")?;
 574                 self.print_type(&ty)?;
 575                 self.s.space()?;
 576                 self.end()?; // end the head-ibox
 577
 578                 self.word_space("=")?;
 579                 self.ann.nested(self, Nested::Body(expr))?;
 580                 self.s.word(";")?;
 581                 self.end()?; // end the outer cbox
 582             }
 583             hir::ItemKind::Const(ref ty, expr) => {
 584                 self.head(&visibility_qualified(&item.vis, "const"))?;
 585                 self.print_name(item.name)?;
 586                 self.word_space(":")?;
 587                 self.print_type(&ty)?;
 588                 self.s.space()?;
 589                 self.end()?; // end the head-ibox
 590
 591                 self.word_space("=")?;
 592                 self.ann.nested(self, Nested::Body(expr))?;
 593                 self.s.word(";")?;
 594                 self.end()?; // end the outer cbox
 595             }
 596             hir::ItemKind::Fn(ref decl, header, ref typarams, body) => {
 597                 self.head("")?;
 598                 self.print_fn(decl,
 599                               header,
 600                               Some(item.name),
 601                               typarams,
 602                               &item.vis,
 603                               &[],
 604                               Some(body))?;
 605                 self.s.word(" ")?;
 606                 self.end()?; // need to close a box
 607                 self.end()?; // need to close a box
 608                 self.ann.nested(self, Nested::Body(body))?;
 609             }
 610             hir::ItemKind::Mod(ref _mod) => {
 611                 self.head(&visibility_qualified(&item.vis, "mod"))?;
 612                 self.print_name(item.name)?;
 613                 self.nbsp()?;
 614                 self.bopen()?;
 615                 self.print_mod(_mod, &item.attrs)?;
 616                 self.bclose(item.span)?;
 617             }
 618             hir::ItemKind::ForeignMod(ref nmod) => {
 619                 self.head("extern")?;
 620                 self.word_nbsp(&nmod.abi.to_string())?;
 621                 self.bopen()?;
 622                 self.print_foreign_mod(nmod, &item.attrs)?;
 623                 self.bclose(item.span)?;
 624             }
 625             hir::ItemKind::GlobalAsm(ref ga) => {
 626                 self.head(&visibility_qualified(&item.vis, "global asm"))?;
 627                 self.s.word(&ga.asm.as_str())?;
 628                 self.end()?
 629             }
 630             hir::ItemKind::Ty(ref ty, ref generics) => {
 631                 self.head(&visibility_qualified(&item.vis, "type"))?;
 632                 self.print_name(item.name)?;
 633                 self.print_generic_params(&generics.params)?;
 634                 self.end()?; // end the inner ibox
 635
 636                 self.print_where_clause(&generics.where_clause)?;
 637                 self.s.space()?;
 638                 self.word_space("=")?;
 639                 self.print_type(&ty)?;
 640                 self.s.word(";")?;
 641                 self.end()?; // end the outer ibox
 642             }
 643             hir::ItemKind::Existential(ref exist) => {
 644                 self.head(&visibility_qualified(&item.vis, "existential type"))?;
 645                 self.print_name(item.name)?;
 646                 self.print_generic_params(&exist.generics.params)?;
 647                 self.end()?; // end the inner ibox
 648
 649                 self.print_where_clause(&exist.generics.where_clause)?;
 650                 self.s.space()?;
 651                 self.word_space(":")?;
 652                 let mut real_bounds = Vec::with_capacity(exist.bounds.len());
 653                 for b in exist.bounds.iter() {
 654                     if let GenericBound::Trait(ref ptr, hir::TraitBoundModifier::Maybe) = *b {
 655                         self.s.space()?;
 656                         self.word_space("for ?")?;
 657                         self.print_trait_ref(&ptr.trait_ref)?;
 658                     } else {
 659                         real_bounds.push(b.clone());
 660                     }
 661                 }
 662                 self.print_bounds(":", &real_bounds[..])?;
 663                 self.s.word(";")?;
 664                 self.end()?; // end the outer ibox
 665             }
 666             hir::ItemKind::Enum(ref enum_definition, ref params) => {
 667                 self.print_enum_def(enum_definition, params, item.name, item.span, &item.vis)?;
 668             }
 669             hir::ItemKind::Struct(ref struct_def, ref generics) => {
 670                 self.head(&visibility_qualified(&item.vis, "struct"))?;
 671                 self.print_struct(struct_def, generics, item.name, item.span, true)?;
 672             }
 673             hir::ItemKind::Union(ref struct_def, ref generics) => {
 674                 self.head(&visibility_qualified(&item.vis, "union"))?;
 675                 self.print_struct(struct_def, generics, item.name, item.span, true)?;
 676             }
 677             hir::ItemKind::Impl(unsafety,
 678                           polarity,
 679                           defaultness,
 680                           ref generics,
 681                           ref opt_trait,
 682                           ref ty,
 683                           ref impl_items) => {
 684                 self.head("")?;
 685                 self.print_visibility(&item.vis)?;
 686                 self.print_defaultness(defaultness)?;
 687                 self.print_unsafety(unsafety)?;
 688                 self.word_nbsp("impl")?;
 689
 690                 if !generics.params.is_empty() {
 691                     self.print_generic_params(&generics.params)?;
 692                     self.s.space()?;
 693                 }
 694
 695                 if let hir::ImplPolarity::Negative = polarity {
 696                     self.s.word("!")?;
 697                 }
 698
 699                 if let Some(ref t) = opt_trait {
 700                     self.print_trait_ref(t)?;
 701                     self.s.space()?;
 702                     self.word_space("for")?;
 703                 }
 704
 705                 self.print_type(&ty)?;
 706                 self.print_where_clause(&generics.where_clause)?;
 707
 708                 self.s.space()?;
 709                 self.bopen()?;
 710                 self.print_inner_attributes(&item.attrs)?;
 711                 for impl_item in impl_items {
 712                     self.ann.nested(self, Nested::ImplItem(impl_item.id))?;
 713                 }
 714                 self.bclose(item.span)?;
 715             }
 716             hir::ItemKind::Trait(is_auto, unsafety, ref generics, ref bounds, ref trait_items) => {
 717                 self.head("")?;
 718                 self.print_visibility(&item.vis)?;
 719                 self.print_is_auto(is_auto)?;
 720                 self.print_unsafety(unsafety)?;
 721                 self.word_nbsp("trait")?;
 722                 self.print_name(item.name)?;
 723                 self.print_generic_params(&generics.params)?;
 724                 let mut real_bounds = Vec::with_capacity(bounds.len());
 725                 for b in bounds.iter() {
 726                     if let GenericBound::Trait(ref ptr, hir::TraitBoundModifier::Maybe) = *b {
 727                         self.s.space()?;
 728                         self.word_space("for ?")?;
 729                         self.print_trait_ref(&ptr.trait_ref)?;
 730                     } else {
 731                         real_bounds.push(b.clone());
 732                     }
 733                 }
 734                 self.print_bounds(":", &real_bounds[..])?;
 735                 self.print_where_clause(&generics.where_clause)?;
 736                 self.s.word(" ")?;
 737                 self.bopen()?;
 738                 for trait_item in trait_items {
 739                     self.ann.nested(self, Nested::TraitItem(trait_item.id))?;
 740                 }
 741                 self.bclose(item.span)?;
 742             }
 743             hir::ItemKind::TraitAlias(ref generics, ref bounds) => {
 744                 self.head("")?;
 745                 self.print_visibility(&item.vis)?;
 746                 self.word_nbsp("trait")?;
 747                 self.print_name(item.name)?;
 748                 self.print_generic_params(&generics.params)?;
 749                 let mut real_bounds = Vec::with_capacity(bounds.len());
 750                 // FIXME(durka) this seems to be some quite outdated syntax
 751                 for b in bounds.iter() {
 752                     if let GenericBound::Trait(ref ptr, hir::TraitBoundModifier::Maybe) = *b {
 753                         self.s.space()?;
 754                         self.word_space("for ?")?;
 755                         self.print_trait_ref(&ptr.trait_ref)?;
 756                     } else {
 757                         real_bounds.push(b.clone());
 758                     }
 759                 }
 760                 self.nbsp()?;
 761                 self.print_bounds("=", &real_bounds[..])?;
 762                 self.print_where_clause(&generics.where_clause)?;
 763                 self.s.word(";")?;
 764             }
 765         }
 766         self.ann.post(self, AnnNode::Item(item))
 767     }
 768
 769     pub fn print_trait_ref(&mut self, t: &hir::TraitRef) -> io::Result<()> {
 770         self.print_path(&t.path, false)
 771     }
 772
 773     fn print_formal_generic_params(
 774         &mut self,
 775         generic_params: &[hir::GenericParam]
 776     ) -> io::Result<()> {
 777         if !generic_params.is_empty() {
 778             self.s.word("for")?;
 779             self.print_generic_params(generic_params)?;
 780             self.nbsp()?;
 781         }
 782         Ok(())
 783     }
 784
 785     fn print_poly_trait_ref(&mut self, t: &hir::PolyTraitRef) -> io::Result<()> {
 786         self.print_formal_generic_params(&t.bound_generic_params)?;
 787         self.print_trait_ref(&t.trait_ref)
 788     }
 789
 790     pub fn print_enum_def(&mut self,
 791                           enum_definition: &hir::EnumDef,
 792                           generics: &hir::Generics,
 793                           name: ast::Name,
 794                           span: syntax_pos::Span,
 795                           visibility: &hir::Visibility)
 796                           -> io::Result<()> {
 797         self.head(&visibility_qualified(visibility, "enum"))?;
 798         self.print_name(name)?;
 799         self.print_generic_params(&generics.params)?;
 800         self.print_where_clause(&generics.where_clause)?;
 801         self.s.space()?;
 802         self.print_variants(&enum_definition.variants, span)
 803     }
 804
 805     pub fn print_variants(&mut self,
 806                           variants: &[hir::Variant],
 807                           span: syntax_pos::Span)
 808                           -> io::Result<()> {
 809         self.bopen()?;
 810         for v in variants {
 811             self.space_if_not_bol()?;
 812             self.maybe_print_comment(v.span.lo())?;
 813             self.print_outer_attributes(&v.node.attrs)?;
 814             self.ibox(indent_unit)?;
 815             self.print_variant(v)?;
 816             self.s.word(",")?;
 817             self.end()?;
 818             self.maybe_print_trailing_comment(v.span, None)?;
 819         }
 820         self.bclose(span)
 821     }
 822
 823     pub fn print_visibility(&mut self, vis: &hir::Visibility) -> io::Result<()> {
 824         match vis.node {
 825             hir::VisibilityKind::Public => self.word_nbsp("pub")?,
 826             hir::VisibilityKind::Crate(ast::CrateSugar::JustCrate) => self.word_nbsp("crate")?,
 827             hir::VisibilityKind::Crate(ast::CrateSugar::PubCrate) => self.word_nbsp("pub(crate)")?,
 828             hir::VisibilityKind::Restricted { ref path, .. } => {
 829                 self.s.word("pub(")?;
 830                 if path.segments.len() == 1 &&
 831                    path.segments[0].ident.name == keywords::Super.name() {
 832                     // Special case: `super` can print like `pub(super)`.
 833                     self.s.word("super")?;
 834                 } else {
 835                     // Everything else requires `in` at present.
 836                     self.word_nbsp("in")?;
 837                     self.print_path(path, false)?;
 838                 }
 839                 self.word_nbsp(")")?;
 840             }
 841             hir::VisibilityKind::Inherited => ()
 842         }
 843
 844         Ok(())
 845     }
 846
 847     pub fn print_defaultness(&mut self, defaultness: hir::Defaultness) -> io::Result<()> {
 848         match defaultness {
 849             hir::Defaultness::Default { .. } => self.word_nbsp("default")?,
 850             hir::Defaultness::Final => (),
 851         }
 852         Ok(())
 853     }
 854
 855     pub fn print_struct(&mut self,
 856                         struct_def: &hir::VariantData,
 857                         generics: &hir::Generics,
 858                         name: ast::Name,
 859                         span: syntax_pos::Span,
 860                         print_finalizer: bool)
 861                         -> io::Result<()> {
 862         self.print_name(name)?;
 863         self.print_generic_params(&generics.params)?;
 864         if !struct_def.is_struct() {
 865             if struct_def.is_tuple() {
 866                 self.popen()?;
 867                 self.commasep(Inconsistent, struct_def.fields(), |s, field| {
 868                     s.maybe_print_comment(field.span.lo())?;
 869                     s.print_outer_attributes(&field.attrs)?;
 870                     s.print_visibility(&field.vis)?;
 871                     s.print_type(&field.ty)
 872                 })?;
 873                 self.pclose()?;
 874             }
 875             self.print_where_clause(&generics.where_clause)?;
 876             if print_finalizer {
 877                 self.s.word(";")?;
 878             }
 879             self.end()?;
 880             self.end() // close the outer-box
 881         } else {
 882             self.print_where_clause(&generics.where_clause)?;
 883             self.nbsp()?;
 884             self.bopen()?;
 885             self.hardbreak_if_not_bol()?;
 886
 887             for field in struct_def.fields() {
 888                 self.hardbreak_if_not_bol()?;
 889                 self.maybe_print_comment(field.span.lo())?;
 890                 self.print_outer_attributes(&field.attrs)?;
 891                 self.print_visibility(&field.vis)?;
 892                 self.print_ident(field.ident)?;
 893                 self.word_nbsp(":")?;
 894                 self.print_type(&field.ty)?;
 895                 self.s.word(",")?;
 896             }
 897
 898             self.bclose(span)
 899         }
 900     }
 901
 902     pub fn print_variant(&mut self, v: &hir::Variant) -> io::Result<()> {
 903         self.head("")?;
 904         let generics = hir::Generics::empty();
 905         self.print_struct(&v.node.data, &generics, v.node.name, v.span, false)?;
 906         if let Some(ref d) = v.node.disr_expr {
 907             self.s.space()?;
 908             self.word_space("=")?;
 909             self.print_anon_const(d)?;
 910         }
 911         Ok(())
 912     }
 913     pub fn print_method_sig(&mut self,
 914                             ident: ast::Ident,
 915                             m: &hir::MethodSig,
 916                             generics: &hir::Generics,
 917                             vis: &hir::Visibility,
 918                             arg_names: &[ast::Ident],
 919                             body_id: Option<hir::BodyId>)
 920                             -> io::Result<()> {
 921         self.print_fn(&m.decl,
 922                       m.header,
 923                       Some(ident.name),
 924                       generics,
 925                       vis,
 926                       arg_names,
 927                       body_id)
 928     }
 929
 930     pub fn print_trait_item(&mut self, ti: &hir::TraitItem) -> io::Result<()> {
 931         self.ann.pre(self, AnnNode::SubItem(ti.id))?;
 932         self.hardbreak_if_not_bol()?;
 933         self.maybe_print_comment(ti.span.lo())?;
 934         self.print_outer_attributes(&ti.attrs)?;
 935         match ti.node {
 936             hir::TraitItemKind::Const(ref ty, default) => {
 937                 let vis = Spanned { span: syntax_pos::DUMMY_SP,
 938                                     node: hir::VisibilityKind::Inherited };
 939                 self.print_associated_const(ti.ident, &ty, default, &vis)?;
 940             }
 941             hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Required(ref arg_names)) => {
 942                 let vis = Spanned { span: syntax_pos::DUMMY_SP,
 943                                     node: hir::VisibilityKind::Inherited };
 944                 self.print_method_sig(ti.ident, sig, &ti.generics, &vis, arg_names, None)?;
 945                 self.s.word(";")?;
 946             }
 947             hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Provided(body)) => {
 948                 let vis = Spanned { span: syntax_pos::DUMMY_SP,
 949                                     node: hir::VisibilityKind::Inherited };
 950                 self.head("")?;
 951                 self.print_method_sig(ti.ident, sig, &ti.generics, &vis, &[], Some(body))?;
 952                 self.nbsp()?;
 953                 self.end()?; // need to close a box
 954                 self.end()?; // need to close a box
 955                 self.ann.nested(self, Nested::Body(body))?;
 956             }
 957             hir::TraitItemKind::Type(ref bounds, ref default) => {
 958                 self.print_associated_type(ti.ident,
 959                                            Some(bounds),
 960                                            default.as_ref().map(|ty| &**ty))?;
 961             }
 962         }
 963         self.ann.post(self, AnnNode::SubItem(ti.id))
 964     }
 965
 966     pub fn print_impl_item(&mut self, ii: &hir::ImplItem) -> io::Result<()> {
 967         self.ann.pre(self, AnnNode::SubItem(ii.id))?;
 968         self.hardbreak_if_not_bol()?;
 969         self.maybe_print_comment(ii.span.lo())?;
 970         self.print_outer_attributes(&ii.attrs)?;
 971         self.print_defaultness(ii.defaultness)?;
 972
 973         match ii.node {
 974             hir::ImplItemKind::Const(ref ty, expr) => {
 975                 self.print_associated_const(ii.ident, &ty, Some(expr), &ii.vis)?;
 976             }
 977             hir::ImplItemKind::Method(ref sig, body) => {
 978                 self.head("")?;
 979                 self.print_method_sig(ii.ident, sig, &ii.generics, &ii.vis, &[], Some(body))?;
 980                 self.nbsp()?;
 981                 self.end()?; // need to close a box
 982                 self.end()?; // need to close a box
 983                 self.ann.nested(self, Nested::Body(body))?;
 984             }
 985             hir::ImplItemKind::Type(ref ty) => {
 986                 self.print_associated_type(ii.ident, None, Some(ty))?;
 987             }
 988             hir::ImplItemKind::Existential(ref bounds) => {
 989                 self.word_space("existential")?;
 990                 self.print_associated_type(ii.ident, Some(bounds), None)?;
 991             }
 992         }
 993         self.ann.post(self, AnnNode::SubItem(ii.id))
 994     }
 995
 996     pub fn print_stmt(&mut self, st: &hir::Stmt) -> io::Result<()> {
 997         self.maybe_print_comment(st.span.lo())?;
 998         match st.node {
 999             hir::StmtKind::Decl(ref decl, _) => {
1000                 self.print_decl(&decl)?;
1001             }
1002             hir::StmtKind::Expr(ref expr, _) => {
1003                 self.space_if_not_bol()?;
1004                 self.print_expr(&expr)?;
1005             }
1006             hir::StmtKind::Semi(ref expr, _) => {
1007                 self.space_if_not_bol()?;
1008                 self.print_expr(&expr)?;
1009                 self.s.word(";")?;
1010             }
1011         }
1012         if stmt_ends_with_semi(&st.node) {
1013             self.s.word(";")?;
1014         }
1015         self.maybe_print_trailing_comment(st.span, None)
1016     }
1017
1018     pub fn print_block(&mut self, blk: &hir::Block) -> io::Result<()> {
1019         self.print_block_with_attrs(blk, &[])
1020     }
1021
1022     pub fn print_block_unclosed(&mut self, blk: &hir::Block) -> io::Result<()> {
1023         self.print_block_unclosed_indent(blk, indent_unit)
1024     }
1025
1026     pub fn print_block_unclosed_indent(&mut self,
1027                                        blk: &hir::Block,
1028                                        indented: usize)
1029                                        -> io::Result<()> {
1030         self.print_block_maybe_unclosed(blk, indented, &[], false)
1031     }
1032
1033     pub fn print_block_with_attrs(&mut self,
1034                                   blk: &hir::Block,
1035                                   attrs: &[ast::Attribute])
1036                                   -> io::Result<()> {
1037         self.print_block_maybe_unclosed(blk, indent_unit, attrs, true)
1038     }
1039
1040     pub fn print_block_maybe_unclosed(&mut self,
1041                                       blk: &hir::Block,
1042                                       indented: usize,
1043                                       attrs: &[ast::Attribute],
1044                                       close_box: bool)
1045                                       -> io::Result<()> {
1046         match blk.rules {
1047             hir::UnsafeBlock(..) => self.word_space("unsafe")?,
1048             hir::PushUnsafeBlock(..) => self.word_space("push_unsafe")?,
1049             hir::PopUnsafeBlock(..) => self.word_space("pop_unsafe")?,
1050             hir::DefaultBlock => (),
1051         }
1052         self.maybe_print_comment(blk.span.lo())?;
1053         self.ann.pre(self, AnnNode::Block(blk))?;
1054         self.bopen()?;
1055
1056         self.print_inner_attributes(attrs)?;
1057
1058         for st in &blk.stmts {
1059             self.print_stmt(st)?;
1060         }
1061         if let Some(ref expr) = blk.expr {
1062             self.space_if_not_bol()?;
1063             self.print_expr(&expr)?;
1064             self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi()))?;
1065         }
1066         self.bclose_maybe_open(blk.span, indented, close_box)?;
1067         self.ann.post(self, AnnNode::Block(blk))
1068     }
1069
1070     fn print_else(&mut self, els: Option<&hir::Expr>) -> io::Result<()> {
1071         match els {
1072             Some(_else) => {
1073                 match _else.node {
1074                     // "another else-if"
1075                     hir::ExprKind::If(ref i, ref then, ref e) => {
1076                         self.cbox(indent_unit - 1)?;
1077                         self.ibox(0)?;
1078                         self.s.word(" else if ")?;
1079                         self.print_expr_as_cond(&i)?;
1080                         self.s.space()?;
1081                         self.print_expr(&then)?;
1082                         self.print_else(e.as_ref().map(|e| &**e))
1083                     }
1084                     // "final else"
1085                     hir::ExprKind::Block(ref b, _) => {
1086                         self.cbox(indent_unit - 1)?;
1087                         self.ibox(0)?;
1088                         self.s.word(" else ")?;
1089                         self.print_block(&b)
1090                     }
1091                     // BLEAH, constraints would be great here
1092                     _ => {
1093                         panic!("print_if saw if with weird alternative");
1094                     }
1095                 }
1096             }
1097             _ => Ok(()),
1098         }
1099     }
1100
1101     pub fn print_if(&mut self,
1102                     test: &hir::Expr,
1103                     blk: &hir::Expr,
1104                     elseopt: Option<&hir::Expr>)
1105                     -> io::Result<()> {
1106         self.head("if")?;
1107         self.print_expr_as_cond(test)?;
1108         self.s.space()?;
1109         self.print_expr(blk)?;
1110         self.print_else(elseopt)
1111     }
1112
1113     pub fn print_if_let(&mut self,
1114                         pat: &hir::Pat,
1115                         expr: &hir::Expr,
1116                         blk: &hir::Block,
1117                         elseopt: Option<&hir::Expr>)
1118                         -> io::Result<()> {
1119         self.head("if let")?;
1120         self.print_pat(pat)?;
1121         self.s.space()?;
1122         self.word_space("=")?;
1123         self.print_expr_as_cond(expr)?;
1124         self.s.space()?;
1125         self.print_block(blk)?;
1126         self.print_else(elseopt)
1127     }
1128
1129     pub fn print_anon_const(&mut self, constant: &hir::AnonConst) -> io::Result<()> {
1130         self.ann.nested(self, Nested::Body(constant.body))
1131     }
1132
1133     fn print_call_post(&mut self, args: &[hir::Expr]) -> io::Result<()> {
1134         self.popen()?;
1135         self.commasep_exprs(Inconsistent, args)?;
1136         self.pclose()
1137     }
1138
1139     pub fn print_expr_maybe_paren(&mut self, expr: &hir::Expr, prec: i8) -> io::Result<()> {
1140         let needs_par = expr.precedence().order() < prec;
1141         if needs_par {
1142             self.popen()?;
1143         }
1144         self.print_expr(expr)?;
1145         if needs_par {
1146             self.pclose()?;
1147         }
1148         Ok(())
1149     }
1150
1151     /// Print an expr using syntax that's acceptable in a condition position, such as the `cond` in
1152     /// `if cond { ... }`.
1153     pub fn print_expr_as_cond(&mut self, expr: &hir::Expr) -> io::Result<()> {
1154         let needs_par = match expr.node {
1155             // These cases need parens due to the parse error observed in #26461: `if return {}`
1156             // parses as the erroneous construct `if (return {})`, not `if (return) {}`.
1157             hir::ExprKind::Closure(..) |
1158             hir::ExprKind::Ret(..) |
1159             hir::ExprKind::Break(..) => true,
1160
1161             _ => contains_exterior_struct_lit(expr),
1162         };
1163
1164         if needs_par {
1165             self.popen()?;
1166         }
1167         self.print_expr(expr)?;
1168         if needs_par {
1169             self.pclose()?;
1170         }
1171         Ok(())
1172     }
1173
1174     fn print_expr_vec(&mut self, exprs: &[hir::Expr]) -> io::Result<()> {
1175         self.ibox(indent_unit)?;
1176         self.s.word("[")?;
1177         self.commasep_exprs(Inconsistent, exprs)?;
1178         self.s.word("]")?;
1179         self.end()
1180     }
1181
1182     fn print_expr_repeat(&mut self, element: &hir::Expr, count: &hir::AnonConst) -> io::Result<()> {
1183         self.ibox(indent_unit)?;
1184         self.s.word("[")?;
1185         self.print_expr(element)?;
1186         self.word_space(";")?;
1187         self.print_anon_const(count)?;
1188         self.s.word("]")?;
1189         self.end()
1190     }
1191
1192     fn print_expr_struct(&mut self,
1193                          qpath: &hir::QPath,
1194                          fields: &[hir::Field],
1195                          wth: &Option<P<hir::Expr>>)
1196                          -> io::Result<()> {
1197         self.print_qpath(qpath, true)?;
1198         self.s.word("{")?;
1199         self.commasep_cmnt(Consistent,
1200                            &fields[..],
1201                            |s, field| {
1202                                s.ibox(indent_unit)?;
1203                                if !field.is_shorthand {
1204                                     s.print_ident(field.ident)?;
1205                                     s.word_space(":")?;
1206                                }
1207                                s.print_expr(&field.expr)?;
1208                                s.end()
1209                            },
1210                            |f| f.span)?;
1211         match *wth {
1212             Some(ref expr) => {
1213                 self.ibox(indent_unit)?;
1214                 if !fields.is_empty() {
1215                     self.s.word(",")?;
1216                     self.s.space()?;
1217                 }
1218                 self.s.word("..")?;
1219                 self.print_expr(&expr)?;
1220                 self.end()?;
1221             }
1222             _ => if !fields.is_empty() {
1223                 self.s.word(",")?
1224             },
1225         }
1226         self.s.word("}")?;
1227         Ok(())
1228     }
1229
1230     fn print_expr_tup(&mut self, exprs: &[hir::Expr]) -> io::Result<()> {
1231         self.popen()?;
1232         self.commasep_exprs(Inconsistent, exprs)?;
1233         if exprs.len() == 1 {
1234             self.s.word(",")?;
1235         }
1236         self.pclose()
1237     }
1238
1239     fn print_expr_call(&mut self, func: &hir::Expr, args: &[hir::Expr]) -> io::Result<()> {
1240         let prec =
1241             match func.node {
1242                 hir::ExprKind::Field(..) => parser::PREC_FORCE_PAREN,
1243                 _ => parser::PREC_POSTFIX,
1244             };
1245
1246         self.print_expr_maybe_paren(func, prec)?;
1247         self.print_call_post(args)
1248     }
1249
1250     fn print_expr_method_call(&mut self,
1251                               segment: &hir::PathSegment,
1252                               args: &[hir::Expr])
1253                               -> io::Result<()> {
1254         let base_args = &args[1..];
1255         self.print_expr_maybe_paren(&args[0], parser::PREC_POSTFIX)?;
1256         self.s.word(".")?;
1257         self.print_ident(segment.ident)?;
1258
1259         segment.with_generic_args(|generic_args| {
1260             if !generic_args.args.is_empty() || !generic_args.bindings.is_empty() {
1261                 return self.print_generic_args(&generic_args, segment.infer_types, true);
1262             }
1263             Ok(())
1264         })?;
1265         self.print_call_post(base_args)
1266     }
1267
1268     fn print_expr_binary(&mut self,
1269                          op: hir::BinOp,
1270                          lhs: &hir::Expr,
1271                          rhs: &hir::Expr)
1272                          -> io::Result<()> {
1273         let assoc_op = bin_op_to_assoc_op(op.node);
1274         let prec = assoc_op.precedence() as i8;
1275         let fixity = assoc_op.fixity();
1276
1277         let (left_prec, right_prec) = match fixity {
1278             Fixity::Left => (prec, prec + 1),
1279             Fixity::Right => (prec + 1, prec),
1280             Fixity::None => (prec + 1, prec + 1),
1281         };
1282
1283         let left_prec = match (&lhs.node, op.node) {
1284             // These cases need parens: `x as i32 < y` has the parser thinking that `i32 < y` is
1285             // the beginning of a path type. It starts trying to parse `x as (i32 < y ...` instead
1286             // of `(x as i32) < ...`. We need to convince it _not_ to do that.
1287             (&hir::ExprKind::Cast { .. }, hir::BinOpKind::Lt) |
1288             (&hir::ExprKind::Cast { .. }, hir::BinOpKind::Shl) => parser::PREC_FORCE_PAREN,
1289             _ => left_prec,
1290         };
1291
1292         self.print_expr_maybe_paren(lhs, left_prec)?;
1293         self.s.space()?;
1294         self.word_space(op.node.as_str())?;
1295         self.print_expr_maybe_paren(rhs, right_prec)
1296     }
1297
1298     fn print_expr_unary(&mut self, op: hir::UnOp, expr: &hir::Expr) -> io::Result<()> {
1299         self.s.word(op.as_str())?;
1300         self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
1301     }
1302
1303     fn print_expr_addr_of(&mut self,
1304                           mutability: hir::Mutability,
1305                           expr: &hir::Expr)
1306                           -> io::Result<()> {
1307         self.s.word("&")?;
1308         self.print_mutability(mutability)?;
1309         self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
1310     }
1311
1312     pub fn print_expr(&mut self, expr: &hir::Expr) -> io::Result<()> {
1313         self.maybe_print_comment(expr.span.lo())?;
1314         self.print_outer_attributes(&expr.attrs)?;
1315         self.ibox(indent_unit)?;
1316         self.ann.pre(self, AnnNode::Expr(expr))?;
1317         match expr.node {
1318             hir::ExprKind::Box(ref expr) => {
1319                 self.word_space("box")?;
1320                 self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)?;
1321             }
1322             hir::ExprKind::Array(ref exprs) => {
1323                 self.print_expr_vec(exprs)?;
1324             }
1325             hir::ExprKind::Repeat(ref element, ref count) => {
1326                 self.print_expr_repeat(&element, count)?;
1327             }
1328             hir::ExprKind::Struct(ref qpath, ref fields, ref wth) => {
1329                 self.print_expr_struct(qpath, &fields[..], wth)?;
1330             }
1331             hir::ExprKind::Tup(ref exprs) => {
1332                 self.print_expr_tup(exprs)?;
1333             }
1334             hir::ExprKind::Call(ref func, ref args) => {
1335                 self.print_expr_call(&func, args)?;
1336             }
1337             hir::ExprKind::MethodCall(ref segment, _, ref args) => {
1338                 self.print_expr_method_call(segment, args)?;
1339             }
1340             hir::ExprKind::Binary(op, ref lhs, ref rhs) => {
1341                 self.print_expr_binary(op, &lhs, &rhs)?;
1342             }
1343             hir::ExprKind::Unary(op, ref expr) => {
1344                 self.print_expr_unary(op, &expr)?;
1345             }
1346             hir::ExprKind::AddrOf(m, ref expr) => {
1347                 self.print_expr_addr_of(m, &expr)?;
1348             }
1349             hir::ExprKind::Lit(ref lit) => {
1350                 self.print_literal(&lit)?;
1351             }
1352             hir::ExprKind::Cast(ref expr, ref ty) => {
1353                 let prec = AssocOp::As.precedence() as i8;
1354                 self.print_expr_maybe_paren(&expr, prec)?;
1355                 self.s.space()?;
1356                 self.word_space("as")?;
1357                 self.print_type(&ty)?;
1358             }
1359             hir::ExprKind::Type(ref expr, ref ty) => {
1360                 let prec = AssocOp::Colon.precedence() as i8;
1361                 self.print_expr_maybe_paren(&expr, prec)?;
1362                 self.word_space(":")?;
1363                 self.print_type(&ty)?;
1364             }
1365             hir::ExprKind::If(ref test, ref blk, ref elseopt) => {
1366                 self.print_if(&test, &blk, elseopt.as_ref().map(|e| &**e))?;
1367             }
1368             hir::ExprKind::While(ref test, ref blk, opt_label) => {
1369                 if let Some(label) = opt_label {
1370                     self.print_ident(label.ident)?;
1371                     self.word_space(":")?;
1372                 }
1373                 self.head("while")?;
1374                 self.print_expr_as_cond(&test)?;
1375                 self.s.space()?;
1376                 self.print_block(&blk)?;
1377             }
1378             hir::ExprKind::Loop(ref blk, opt_label, _) => {
1379                 if let Some(label) = opt_label {
1380                     self.print_ident(label.ident)?;
1381                     self.word_space(":")?;
1382                 }
1383                 self.head("loop")?;
1384                 self.s.space()?;
1385                 self.print_block(&blk)?;
1386             }
1387             hir::ExprKind::Match(ref expr, ref arms, _) => {
1388                 self.cbox(indent_unit)?;
1389                 self.ibox(4)?;
1390                 self.word_nbsp("match")?;
1391                 self.print_expr_as_cond(&expr)?;
1392                 self.s.space()?;
1393                 self.bopen()?;
1394                 for arm in arms {
1395                     self.print_arm(arm)?;
1396                 }
1397                 self.bclose_(expr.span, indent_unit)?;
1398             }
1399             hir::ExprKind::Closure(capture_clause, ref decl, body, _fn_decl_span, _gen) => {
1400                 self.print_capture_clause(capture_clause)?;
1401
1402                 self.print_closure_args(&decl, body)?;
1403                 self.s.space()?;
1404
1405                 // this is a bare expression
1406                 self.ann.nested(self, Nested::Body(body))?;
1407                 self.end()?; // need to close a box
1408
1409                 // a box will be closed by print_expr, but we didn't want an overall
1410                 // wrapper so we closed the corresponding opening. so create an
1411                 // empty box to satisfy the close.
1412                 self.ibox(0)?;
1413             }
1414             hir::ExprKind::Block(ref blk, opt_label) => {
1415                 if let Some(label) = opt_label {
1416                     self.print_ident(label.ident)?;
1417                     self.word_space(":")?;
1418                 }
1419                 // containing cbox, will be closed by print-block at }
1420                 self.cbox(indent_unit)?;
1421                 // head-box, will be closed by print-block after {
1422                 self.ibox(0)?;
1423                 self.print_block(&blk)?;
1424             }
1425             hir::ExprKind::Assign(ref lhs, ref rhs) => {
1426                 let prec = AssocOp::Assign.precedence() as i8;
1427                 self.print_expr_maybe_paren(&lhs, prec + 1)?;
1428                 self.s.space()?;
1429                 self.word_space("=")?;
1430                 self.print_expr_maybe_paren(&rhs, prec)?;
1431             }
1432             hir::ExprKind::AssignOp(op, ref lhs, ref rhs) => {
1433                 let prec = AssocOp::Assign.precedence() as i8;
1434                 self.print_expr_maybe_paren(&lhs, prec + 1)?;
1435                 self.s.space()?;
1436                 self.s.word(op.node.as_str())?;
1437                 self.word_space("=")?;
1438                 self.print_expr_maybe_paren(&rhs, prec)?;
1439             }
1440             hir::ExprKind::Field(ref expr, ident) => {
1441                 self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX)?;
1442                 self.s.word(".")?;
1443                 self.print_ident(ident)?;
1444             }
1445             hir::ExprKind::Index(ref expr, ref index) => {
1446                 self.print_expr_maybe_paren(&expr, parser::PREC_POSTFIX)?;
1447                 self.s.word("[")?;
1448                 self.print_expr(&index)?;
1449                 self.s.word("]")?;
1450             }
1451             hir::ExprKind::Path(ref qpath) => {
1452                 self.print_qpath(qpath, true)?
1453             }
1454             hir::ExprKind::Break(destination, ref opt_expr) => {
1455                 self.s.word("break")?;
1456                 self.s.space()?;
1457                 if let Some(label) = destination.label {
1458                     self.print_ident(label.ident)?;
1459                     self.s.space()?;
1460                 }
1461                 if let Some(ref expr) = *opt_expr {
1462                     self.print_expr_maybe_paren(expr, parser::PREC_JUMP)?;
1463                     self.s.space()?;
1464                 }
1465             }
1466             hir::ExprKind::Continue(destination) => {
1467                 self.s.word("continue")?;
1468                 self.s.space()?;
1469                 if let Some(label) = destination.label {
1470                     self.print_ident(label.ident)?;
1471                     self.s.space()?
1472                 }
1473             }
1474             hir::ExprKind::Ret(ref result) => {
1475                 self.s.word("return")?;
1476                 if let Some(ref expr) = *result {
1477                     self.s.word(" ")?;
1478                     self.print_expr_maybe_paren(&expr, parser::PREC_JUMP)?;
1479                 }
1480             }
1481             hir::ExprKind::InlineAsm(ref a, ref outputs, ref inputs) => {
1482                 self.s.word("asm!")?;
1483                 self.popen()?;
1484                 self.print_string(&a.asm.as_str(), a.asm_str_style)?;
1485                 self.word_space(":")?;
1486
1487                 let mut out_idx = 0;
1488                 self.commasep(Inconsistent, &a.outputs, |s, out| {
1489                     let constraint = out.constraint.as_str();
1490                     let mut ch = constraint.chars();
1491                     match ch.next() {
1492                         Some('=') if out.is_rw => {
1493                             s.print_string(&format!("+{}", ch.as_str()),
1494                                            ast::StrStyle::Cooked)?
1495                         }
1496                         _ => s.print_string(&constraint, ast::StrStyle::Cooked)?,
1497                     }
1498                     s.popen()?;
1499                     s.print_expr(&outputs[out_idx])?;
1500                     s.pclose()?;
1501                     out_idx += 1;
1502                     Ok(())
1503                 })?;
1504                 self.s.space()?;
1505                 self.word_space(":")?;
1506
1507                 let mut in_idx = 0;
1508                 self.commasep(Inconsistent, &a.inputs, |s, co| {
1509                     s.print_string(&co.as_str(), ast::StrStyle::Cooked)?;
1510                     s.popen()?;
1511                     s.print_expr(&inputs[in_idx])?;
1512                     s.pclose()?;
1513                     in_idx += 1;
1514                     Ok(())
1515                 })?;
1516                 self.s.space()?;
1517                 self.word_space(":")?;
1518
1519                 self.commasep(Inconsistent, &a.clobbers, |s, co| {
1520                     s.print_string(&co.as_str(), ast::StrStyle::Cooked)?;
1521                     Ok(())
1522                 })?;
1523
1524                 let mut options = vec![];
1525                 if a.volatile {
1526                     options.push("volatile");
1527                 }
1528                 if a.alignstack {
1529                     options.push("alignstack");
1530                 }
1531                 if a.dialect == ast::AsmDialect::Intel {
1532                     options.push("intel");
1533                 }
1534
1535                 if !options.is_empty() {
1536                     self.s.space()?;
1537                     self.word_space(":")?;
1538                     self.commasep(Inconsistent, &options, |s, &co| {
1539                         s.print_string(co, ast::StrStyle::Cooked)?;
1540                         Ok(())
1541                     })?;
1542                 }
1543
1544                 self.pclose()?;
1545             }
1546             hir::ExprKind::Yield(ref expr) => {
1547                 self.word_space("yield")?;
1548                 self.print_expr_maybe_paren(&expr, parser::PREC_JUMP)?;
1549             }
1550         }
1551         self.ann.post(self, AnnNode::Expr(expr))?;
1552         self.end()
1553     }
1554
1555     pub fn print_local_decl(&mut self, loc: &hir::Local) -> io::Result<()> {
1556         self.print_pat(&loc.pat)?;
1557         if let Some(ref ty) = loc.ty {
1558             self.word_space(":")?;
1559             self.print_type(&ty)?;
1560         }
1561         Ok(())
1562     }
1563
1564     pub fn print_decl(&mut self, decl: &hir::Decl) -> io::Result<()> {
1565         self.maybe_print_comment(decl.span.lo())?;
1566         match decl.node {
1567             hir::DeclKind::Local(ref loc) => {
1568                 self.space_if_not_bol()?;
1569                 self.ibox(indent_unit)?;
1570                 self.word_nbsp("let")?;
1571
1572                 self.ibox(indent_unit)?;
1573                 self.print_local_decl(&loc)?;
1574                 self.end()?;
1575                 if let Some(ref init) = loc.init {
1576                     self.nbsp()?;
1577                     self.word_space("=")?;
1578                     self.print_expr(&init)?;
1579                 }
1580                 self.end()
1581             }
1582             hir::DeclKind::Item(item) => {
1583                 self.ann.nested(self, Nested::Item(item))
1584             }
1585         }
1586     }
1587
1588     pub fn print_usize(&mut self, i: usize) -> io::Result<()> {
1589         self.s.word(&i.to_string())
1590     }
1591
1592     pub fn print_ident(&mut self, ident: ast::Ident) -> io::Result<()> {
1593         if ident.is_raw_guess() {
1594             self.s.word(&format!("r#{}", ident.name))?;
1595         } else {
1596             self.s.word(&ident.as_str())?;
1597         }
1598         self.ann.post(self, AnnNode::Name(&ident.name))
1599     }
1600
1601     pub fn print_name(&mut self, name: ast::Name) -> io::Result<()> {
1602         self.print_ident(ast::Ident::with_empty_ctxt(name))
1603     }
1604
1605     pub fn print_for_decl(&mut self, loc: &hir::Local, coll: &hir::Expr) -> io::Result<()> {
1606         self.print_local_decl(loc)?;
1607         self.s.space()?;
1608         self.word_space("in")?;
1609         self.print_expr(coll)
1610     }
1611
1612     pub fn print_path(&mut self,
1613                       path: &hir::Path,
1614                       colons_before_params: bool)
1615                       -> io::Result<()> {
1616         self.maybe_print_comment(path.span.lo())?;
1617
1618         for (i, segment) in path.segments.iter().enumerate() {
1619             if i > 0 {
1620                 self.s.word("::")?
1621             }
1622             if segment.ident.name != keywords::CrateRoot.name() &&
1623                segment.ident.name != keywords::DollarCrate.name() {
1624                self.print_ident(segment.ident)?;
1625                segment.with_generic_args(|generic_args| {
1626                    self.print_generic_args(generic_args, segment.infer_types,
1627                                            colons_before_params)
1628                })?;
1629             }
1630         }
1631
1632         Ok(())
1633     }
1634
1635     pub fn print_qpath(&mut self,
1636                        qpath: &hir::QPath,
1637                        colons_before_params: bool)
1638                        -> io::Result<()> {
1639         match *qpath {
1640             hir::QPath::Resolved(None, ref path) => {
1641                 self.print_path(path, colons_before_params)
1642             }
1643             hir::QPath::Resolved(Some(ref qself), ref path) => {
1644                 self.s.word("<")?;
1645                 self.print_type(qself)?;
1646                 self.s.space()?;
1647                 self.word_space("as")?;
1648
1649                 for (i, segment) in path.segments[..path.segments.len() - 1].iter().enumerate() {
1650                     if i > 0 {
1651                         self.s.word("::")?
1652                     }
1653                     if segment.ident.name != keywords::CrateRoot.name() &&
1654                        segment.ident.name != keywords::DollarCrate.name() {
1655                         self.print_ident(segment.ident)?;
1656                         segment.with_generic_args(|generic_args| {
1657                             self.print_generic_args(generic_args,
1658                                                     segment.infer_types,
1659                                                     colons_before_params)
1660                         })?;
1661                     }
1662                 }
1663
1664                 self.s.word(">")?;
1665                 self.s.word("::")?;
1666                 let item_segment = path.segments.last().unwrap();
1667                 self.print_ident(item_segment.ident)?;
1668                 item_segment.with_generic_args(|generic_args| {
1669                     self.print_generic_args(generic_args,
1670                                             item_segment.infer_types,
1671                                             colons_before_params)
1672                 })
1673             }
1674             hir::QPath::TypeRelative(ref qself, ref item_segment) => {
1675                 self.s.word("<")?;
1676                 self.print_type(qself)?;
1677                 self.s.word(">")?;
1678                 self.s.word("::")?;
1679                 self.print_ident(item_segment.ident)?;
1680                 item_segment.with_generic_args(|generic_args| {
1681                     self.print_generic_args(generic_args,
1682                                             item_segment.infer_types,
1683                                             colons_before_params)
1684                 })
1685             }
1686         }
1687     }
1688
1689     fn print_generic_args(&mut self,
1690                              generic_args: &hir::GenericArgs,
1691                              infer_types: bool,
1692                              colons_before_params: bool)
1693                              -> io::Result<()> {
1694         if generic_args.parenthesized {
1695             self.s.word("(")?;
1696             self.commasep(Inconsistent, generic_args.inputs(), |s, ty| s.print_type(&ty))?;
1697             self.s.word(")")?;
1698
1699             self.space_if_not_bol()?;
1700             self.word_space("->")?;
1701             self.print_type(&generic_args.bindings[0].ty)?;
1702         } else {
1703             let start = if colons_before_params { "::<" } else { "<" };
1704             let empty = Cell::new(true);
1705             let start_or_comma = |this: &mut Self| {
1706                 if empty.get() {
1707                     empty.set(false);
1708                     this.s.word(start)
1709                 } else {
1710                     this.word_space(",")
1711                 }
1712             };
1713
1714             let mut types = vec![];
1715             let mut elide_lifetimes = true;
1716             for arg in &generic_args.args {
1717                 match arg {
1718                     GenericArg::Lifetime(lt) => {
1719                         if !lt.is_elided() {
1720                             elide_lifetimes = false;
1721                         }
1722                     }
1723                     GenericArg::Type(ty) => {
1724                         types.push(ty);
1725                     }
1726                 }
1727             }
1728             if !elide_lifetimes {
1729                 start_or_comma(self)?;
1730                 self.commasep(Inconsistent, &generic_args.args, |s, generic_arg| {
1731                     match generic_arg {
1732                         GenericArg::Lifetime(lt) => s.print_lifetime(lt),
1733                         GenericArg::Type(ty) => s.print_type(ty),
1734                     }
1735                 })?;
1736             } else if !types.is_empty() {
1737                 start_or_comma(self)?;
1738                 self.commasep(Inconsistent, &types, |s, ty| s.print_type(&ty))?;
1739             }
1740
1741             // FIXME(eddyb) This would leak into error messages, e.g.:
1742             // "non-exhaustive patterns: `Some::<..>(_)` not covered".
1743             if infer_types && false {
1744                 start_or_comma(self)?;
1745                 self.s.word("..")?;
1746             }
1747
1748             for binding in generic_args.bindings.iter() {
1749                 start_or_comma(self)?;
1750                 self.print_ident(binding.ident)?;
1751                 self.s.space()?;
1752                 self.word_space("=")?;
1753                 self.print_type(&binding.ty)?;
1754             }
1755
1756             if !empty.get() {
1757                 self.s.word(">")?
1758             }
1759         }
1760
1761         Ok(())
1762     }
1763
1764     pub fn print_pat(&mut self, pat: &hir::Pat) -> io::Result<()> {
1765         self.maybe_print_comment(pat.span.lo())?;
1766         self.ann.pre(self, AnnNode::Pat(pat))?;
1767         // Pat isn't normalized, but the beauty of it
1768         // is that it doesn't matter
1769         match pat.node {
1770             PatKind::Wild => self.s.word("_")?,
1771             PatKind::Binding(binding_mode, _, ident, ref sub) => {
1772                 match binding_mode {
1773                     hir::BindingAnnotation::Ref => {
1774                         self.word_nbsp("ref")?;
1775                         self.print_mutability(hir::MutImmutable)?;
1776                     }
1777                     hir::BindingAnnotation::RefMut => {
1778                         self.word_nbsp("ref")?;
1779                         self.print_mutability(hir::MutMutable)?;
1780                     }
1781                     hir::BindingAnnotation::Unannotated => {}
1782                     hir::BindingAnnotation::Mutable => {
1783                         self.word_nbsp("mut")?;
1784                     }
1785                 }
1786                 self.print_ident(ident)?;
1787                 if let Some(ref p) = *sub {
1788                     self.s.word("@")?;
1789                     self.print_pat(&p)?;
1790                 }
1791             }
1792             PatKind::TupleStruct(ref qpath, ref elts, ddpos) => {
1793                 self.print_qpath(qpath, true)?;
1794                 self.popen()?;
1795                 if let Some(ddpos) = ddpos {
1796                     self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(&p))?;
1797                     if ddpos != 0 {
1798                         self.word_space(",")?;
1799                     }
1800                     self.s.word("..")?;
1801                     if ddpos != elts.len() {
1802                         self.s.word(",")?;
1803                         self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(&p))?;
1804                     }
1805                 } else {
1806                     self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(&p))?;
1807                 }
1808                 self.pclose()?;
1809             }
1810             PatKind::Path(ref qpath) => {
1811                 self.print_qpath(qpath, true)?;
1812             }
1813             PatKind::Struct(ref qpath, ref fields, etc) => {
1814                 self.print_qpath(qpath, true)?;
1815                 self.nbsp()?;
1816                 self.word_space("{")?;
1817                 self.commasep_cmnt(Consistent,
1818                                    &fields[..],
1819                                    |s, f| {
1820                                        s.cbox(indent_unit)?;
1821                                        if !f.node.is_shorthand {
1822                                            s.print_ident(f.node.ident)?;
1823                                            s.word_nbsp(":")?;
1824                                        }
1825                                        s.print_pat(&f.node.pat)?;
1826                                        s.end()
1827                                    },
1828                                    |f| f.node.pat.span)?;
1829                 if etc {
1830                     if !fields.is_empty() {
1831                         self.word_space(",")?;
1832                     }
1833                     self.s.word("..")?;
1834                 }
1835                 self.s.space()?;
1836                 self.s.word("}")?;
1837             }
1838             PatKind::Tuple(ref elts, ddpos) => {
1839                 self.popen()?;
1840                 if let Some(ddpos) = ddpos {
1841                     self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(&p))?;
1842                     if ddpos != 0 {
1843                         self.word_space(",")?;
1844                     }
1845                     self.s.word("..")?;
1846                     if ddpos != elts.len() {
1847                         self.s.word(",")?;
1848                         self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(&p))?;
1849                     }
1850                 } else {
1851                     self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(&p))?;
1852                     if elts.len() == 1 {
1853                         self.s.word(",")?;
1854                     }
1855                 }
1856                 self.pclose()?;
1857             }
1858             PatKind::Box(ref inner) => {
1859                 let is_range_inner = match inner.node {
1860                     PatKind::Range(..) => true,
1861                     _ => false,
1862                 };
1863                 self.s.word("box ")?;
1864                 if is_range_inner {
1865                     self.popen()?;
1866                 }
1867                 self.print_pat(&inner)?;
1868                 if is_range_inner {
1869                     self.pclose()?;
1870                 }
1871             }
1872             PatKind::Ref(ref inner, mutbl) => {
1873                 let is_range_inner = match inner.node {
1874                     PatKind::Range(..) => true,
1875                     _ => false,
1876                 };
1877                 self.s.word("&")?;
1878                 if mutbl == hir::MutMutable {
1879                     self.s.word("mut ")?;
1880                 }
1881                 if is_range_inner {
1882                     self.popen()?;
1883                 }
1884                 self.print_pat(&inner)?;
1885                 if is_range_inner {
1886                     self.pclose()?;
1887                 }
1888             }
1889             PatKind::Lit(ref e) => self.print_expr(&e)?,
1890             PatKind::Range(ref begin, ref end, ref end_kind) => {
1891                 self.print_expr(&begin)?;
1892                 self.s.space()?;
1893                 match *end_kind {
1894                     RangeEnd::Included => self.s.word("...")?,
1895                     RangeEnd::Excluded => self.s.word("..")?,
1896                 }
1897                 self.print_expr(&end)?;
1898             }
1899             PatKind::Slice(ref before, ref slice, ref after) => {
1900                 self.s.word("[")?;
1901                 self.commasep(Inconsistent, &before[..], |s, p| s.print_pat(&p))?;
1902                 if let Some(ref p) = *slice {
1903                     if !before.is_empty() {
1904                         self.word_space(",")?;
1905                     }
1906                     if let PatKind::Wild = p.node {
1907                         // Print nothing
1908                     } else {
1909                         self.print_pat(&p)?;
1910                     }
1911                     self.s.word("..")?;
1912                     if !after.is_empty() {
1913                         self.word_space(",")?;
1914                     }
1915                 }
1916                 self.commasep(Inconsistent, &after[..], |s, p| s.print_pat(&p))?;
1917                 self.s.word("]")?;
1918             }
1919         }
1920         self.ann.post(self, AnnNode::Pat(pat))
1921     }
1922
1923     fn print_arm(&mut self, arm: &hir::Arm) -> io::Result<()> {
1924         // I have no idea why this check is necessary, but here it
1925         // is :(
1926         if arm.attrs.is_empty() {
1927             self.s.space()?;
1928         }
1929         self.cbox(indent_unit)?;
1930         self.ibox(0)?;
1931         self.print_outer_attributes(&arm.attrs)?;
1932         let mut first = true;
1933         for p in &arm.pats {
1934             if first {
1935                 first = false;
1936             } else {
1937                 self.s.space()?;
1938                 self.word_space("|")?;
1939             }
1940             self.print_pat(&p)?;
1941         }
1942         self.s.space()?;
1943         if let Some(ref g) = arm.guard {
1944             match g {
1945                 hir::Guard::If(e) => {
1946                     self.word_space("if")?;
1947                     self.print_expr(&e)?;
1948                     self.s.space()?;
1949                 }
1950             }
1951         }
1952         self.word_space("=>")?;
1953
1954         match arm.body.node {
1955             hir::ExprKind::Block(ref blk, opt_label) => {
1956                 if let Some(label) = opt_label {
1957                     self.print_ident(label.ident)?;
1958                     self.word_space(":")?;
1959                 }
1960                 // the block will close the pattern's ibox
1961                 self.print_block_unclosed_indent(&blk, indent_unit)?;
1962
1963                 // If it is a user-provided unsafe block, print a comma after it
1964                 if let hir::UnsafeBlock(hir::UserProvided) = blk.rules {
1965                     self.s.word(",")?;
1966                 }
1967             }
1968             _ => {
1969                 self.end()?; // close the ibox for the pattern
1970                 self.print_expr(&arm.body)?;
1971                 self.s.word(",")?;
1972             }
1973         }
1974         self.end() // close enclosing cbox
1975     }
1976
1977     pub fn print_fn(&mut self,
1978                     decl: &hir::FnDecl,
1979                     header: hir::FnHeader,
1980                     name: Option<ast::Name>,
1981                     generics: &hir::Generics,
1982                     vis: &hir::Visibility,
1983                     arg_names: &[ast::Ident],
1984                     body_id: Option<hir::BodyId>)
1985                     -> io::Result<()> {
1986         self.print_fn_header_info(header, vis)?;
1987
1988         if let Some(name) = name {
1989             self.nbsp()?;
1990             self.print_name(name)?;
1991         }
1992         self.print_generic_params(&generics.params)?;
1993
1994         self.popen()?;
1995         let mut i = 0;
1996         // Make sure we aren't supplied *both* `arg_names` and `body_id`.
1997         assert!(arg_names.is_empty() || body_id.is_none());
1998         self.commasep(Inconsistent, &decl.inputs, |s, ty| {
1999             s.ibox(indent_unit)?;
2000             if let Some(arg_name) = arg_names.get(i) {
2001                 s.s.word(&arg_name.as_str())?;
2002                 s.s.word(":")?;
2003                 s.s.space()?;
2004             } else if let Some(body_id) = body_id {
2005                 s.ann.nested(s, Nested::BodyArgPat(body_id, i))?;
2006                 s.s.word(":")?;
2007                 s.s.space()?;
2008             }
2009             i += 1;
2010             s.print_type(ty)?;
2011             s.end()
2012         })?;
2013         if decl.variadic {
2014             self.s.word(", ...")?;
2015         }
2016         self.pclose()?;
2017
2018         self.print_fn_output(decl)?;
2019         self.print_where_clause(&generics.where_clause)
2020     }
2021
2022     fn print_closure_args(&mut self, decl: &hir::FnDecl, body_id: hir::BodyId) -> io::Result<()> {
2023         self.s.word("|")?;
2024         let mut i = 0;
2025         self.commasep(Inconsistent, &decl.inputs, |s, ty| {
2026             s.ibox(indent_unit)?;
2027
2028             s.ann.nested(s, Nested::BodyArgPat(body_id, i))?;
2029             i += 1;
2030
2031             if let hir::TyKind::Infer = ty.node {
2032                 // Print nothing
2033             } else {
2034                 s.s.word(":")?;
2035                 s.s.space()?;
2036                 s.print_type(ty)?;
2037             }
2038             s.end()
2039         })?;
2040         self.s.word("|")?;
2041
2042         if let hir::DefaultReturn(..) = decl.output {
2043             return Ok(());
2044         }
2045
2046         self.space_if_not_bol()?;
2047         self.word_space("->")?;
2048         match decl.output {
2049             hir::Return(ref ty) => {
2050                 self.print_type(&ty)?;
2051                 self.maybe_print_comment(ty.span.lo())
2052             }
2053             hir::DefaultReturn(..) => unreachable!(),
2054         }
2055     }
2056
2057     pub fn print_capture_clause(&mut self, capture_clause: hir::CaptureClause) -> io::Result<()> {
2058         match capture_clause {
2059             hir::CaptureByValue => self.word_space("move"),
2060             hir::CaptureByRef => Ok(()),
2061         }
2062     }
2063
2064     pub fn print_bounds(&mut self, prefix: &str, bounds: &[hir::GenericBound]) -> io::Result<()> {
2065         if !bounds.is_empty() {
2066             self.s.word(prefix)?;
2067             let mut first = true;
2068             for bound in bounds {
2069                 if !(first && prefix.is_empty()) {
2070                     self.nbsp()?;
2071                 }
2072                 if first {
2073                     first = false;
2074                 } else {
2075                     self.word_space("+")?;
2076                 }
2077
2078                 match bound {
2079                     GenericBound::Trait(tref, modifier) => {
2080                         if modifier == &TraitBoundModifier::Maybe {
2081                             self.s.word("?")?;
2082                         }
2083                         self.print_poly_trait_ref(tref)?;
2084                     }
2085                     GenericBound::Outlives(lt) => {
2086                         self.print_lifetime(lt)?;
2087                     }
2088                 }
2089             }
2090         }
2091         Ok(())
2092     }
2093
2094     pub fn print_generic_params(&mut self, generic_params: &[GenericParam]) -> io::Result<()> {
2095         if !generic_params.is_empty() {
2096             self.s.word("<")?;
2097
2098             self.commasep(Inconsistent, generic_params, |s, param| {
2099                 s.print_generic_param(param)
2100             })?;
2101
2102             self.s.word(">")?;
2103         }
2104         Ok(())
2105     }
2106
2107     pub fn print_generic_param(&mut self, param: &GenericParam) -> io::Result<()> {
2108         self.print_ident(param.name.ident())?;
2109         match param.kind {
2110             GenericParamKind::Lifetime { .. } => {
2111                 let mut sep = ":";
2112                 for bound in &param.bounds {
2113                     match bound {
2114                         GenericBound::Outlives(lt) => {
2115                             self.s.word(sep)?;
2116                             self.print_lifetime(lt)?;
2117                             sep = "+";
2118                         }
2119                         _ => bug!(),
2120                     }
2121                 }
2122                 Ok(())
2123             }
2124             GenericParamKind::Type { ref default, .. } => {
2125                 self.print_bounds(":", &param.bounds)?;
2126                 match default {
2127                     Some(default) => {
2128                         self.s.space()?;
2129                         self.word_space("=")?;
2130                         self.print_type(&default)
2131                     }
2132                     _ => Ok(()),
2133                 }
2134             }
2135         }
2136     }
2137
2138     pub fn print_lifetime(&mut self, lifetime: &hir::Lifetime) -> io::Result<()> {
2139         self.print_ident(lifetime.name.ident())
2140     }
2141
2142     pub fn print_where_clause(&mut self, where_clause: &hir::WhereClause) -> io::Result<()> {
2143         if where_clause.predicates.is_empty() {
2144             return Ok(());
2145         }
2146
2147         self.s.space()?;
2148         self.word_space("where")?;
2149
2150         for (i, predicate) in where_clause.predicates.iter().enumerate() {
2151             if i != 0 {
2152                 self.word_space(",")?;
2153             }
2154
2155             match predicate {
2156                 &hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
2157                     ref bound_generic_params,
2158                     ref bounded_ty,
2159                     ref bounds,
2160                     ..
2161                 }) => {
2162                     self.print_formal_generic_params(bound_generic_params)?;
2163                     self.print_type(&bounded_ty)?;
2164                     self.print_bounds(":", bounds)?;
2165                 }
2166                 &hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate{ref lifetime,
2167                                                                                 ref bounds,
2168                                                                                 ..}) => {
2169                     self.print_lifetime(lifetime)?;
2170                     self.s.word(":")?;
2171
2172                     for (i, bound) in bounds.iter().enumerate() {
2173                         match bound {
2174                             GenericBound::Outlives(lt) => {
2175                                 self.print_lifetime(lt)?;
2176                             }
2177                             _ => bug!(),
2178                         }
2179
2180                         if i != 0 {
2181                             self.s.word(":")?;
2182                         }
2183                     }
2184                 }
2185                 &hir::WherePredicate::EqPredicate(hir::WhereEqPredicate{ref lhs_ty,
2186                                                                         ref rhs_ty,
2187                                                                         ..}) => {
2188                     self.print_type(lhs_ty)?;
2189                     self.s.space()?;
2190                     self.word_space("=")?;
2191                     self.print_type(rhs_ty)?;
2192                 }
2193             }
2194         }
2195
2196         Ok(())
2197     }
2198
2199     pub fn print_mutability(&mut self, mutbl: hir::Mutability) -> io::Result<()> {
2200         match mutbl {
2201             hir::MutMutable => self.word_nbsp("mut"),
2202             hir::MutImmutable => Ok(()),
2203         }
2204     }
2205
2206     pub fn print_mt(&mut self, mt: &hir::MutTy) -> io::Result<()> {
2207         self.print_mutability(mt.mutbl)?;
2208         self.print_type(&mt.ty)
2209     }
2210
2211     pub fn print_fn_output(&mut self, decl: &hir::FnDecl) -> io::Result<()> {
2212         if let hir::DefaultReturn(..) = decl.output {
2213             return Ok(());
2214         }
2215
2216         self.space_if_not_bol()?;
2217         self.ibox(indent_unit)?;
2218         self.word_space("->")?;
2219         match decl.output {
2220             hir::DefaultReturn(..) => unreachable!(),
2221             hir::Return(ref ty) => self.print_type(&ty)?,
2222         }
2223         self.end()?;
2224
2225         match decl.output {
2226             hir::Return(ref output) => self.maybe_print_comment(output.span.lo()),
2227             _ => Ok(()),
2228         }
2229     }
2230
2231     pub fn print_ty_fn(&mut self,
2232                        abi: Abi,
2233                        unsafety: hir::Unsafety,
2234                        decl: &hir::FnDecl,
2235                        name: Option<ast::Name>,
2236                        generic_params: &[hir::GenericParam],
2237                        arg_names: &[ast::Ident])
2238                        -> io::Result<()> {
2239         self.ibox(indent_unit)?;
2240         if !generic_params.is_empty() {
2241             self.s.word("for")?;
2242             self.print_generic_params(generic_params)?;
2243         }
2244         let generics = hir::Generics {
2245             params: hir::HirVec::new(),
2246             where_clause: hir::WhereClause {
2247                 id: ast::DUMMY_NODE_ID,
2248                 predicates: hir::HirVec::new(),
2249             },
2250             span: syntax_pos::DUMMY_SP,
2251         };
2252         self.print_fn(decl,
2253                       hir::FnHeader {
2254                           unsafety,
2255                           abi,
2256                           constness: hir::Constness::NotConst,
2257                           asyncness: hir::IsAsync::NotAsync,
2258                       },
2259                       name,
2260                       &generics,
2261                       &Spanned { span: syntax_pos::DUMMY_SP,
2262                                  node: hir::VisibilityKind::Inherited },
2263                       arg_names,
2264                       None)?;
2265         self.end()
2266     }
2267
2268     pub fn maybe_print_trailing_comment(&mut self,
2269                                         span: syntax_pos::Span,
2270                                         next_pos: Option<BytePos>)
2271                                         -> io::Result<()> {
2272         let cm = match self.cm {
2273             Some(cm) => cm,
2274             _ => return Ok(()),
2275         };
2276         if let Some(ref cmnt) = self.next_comment() {
2277             if (*cmnt).style != comments::Trailing {
2278                 return Ok(());
2279             }
2280             let span_line = cm.lookup_char_pos(span.hi());
2281             let comment_line = cm.lookup_char_pos((*cmnt).pos);
2282             let mut next = (*cmnt).pos + BytePos(1);
2283             if let Some(p) = next_pos {
2284                 next = p;
2285             }
2286             if span.hi() < (*cmnt).pos && (*cmnt).pos < next &&
2287                span_line.line == comment_line.line {
2288                 self.print_comment(cmnt)?;
2289             }
2290         }
2291         Ok(())
2292     }
2293
2294     pub fn print_remaining_comments(&mut self) -> io::Result<()> {
2295         // If there aren't any remaining comments, then we need to manually
2296         // make sure there is a line break at the end.
2297         if self.next_comment().is_none() {
2298             self.s.hardbreak()?;
2299         }
2300         while let Some(ref cmnt) = self.next_comment() {
2301             self.print_comment(cmnt)?
2302         }
2303         Ok(())
2304     }
2305
2306     pub fn print_opt_abi_and_extern_if_nondefault(&mut self,
2307                                                   opt_abi: Option<Abi>)
2308                                                   -> io::Result<()> {
2309         match opt_abi {
2310             Some(Abi::Rust) => Ok(()),
2311             Some(abi) => {
2312                 self.word_nbsp("extern")?;
2313                 self.word_nbsp(&abi.to_string())
2314             }
2315             None => Ok(()),
2316         }
2317     }
2318
2319     pub fn print_extern_opt_abi(&mut self, opt_abi: Option<Abi>) -> io::Result<()> {
2320         match opt_abi {
2321             Some(abi) => {
2322                 self.word_nbsp("extern")?;
2323                 self.word_nbsp(&abi.to_string())
2324             }
2325             None => Ok(()),
2326         }
2327     }
2328
2329     pub fn print_fn_header_info(&mut self,
2330                                 header: hir::FnHeader,
2331                                 vis: &hir::Visibility)
2332                                 -> io::Result<()> {
2333         self.s.word(&visibility_qualified(vis, ""))?;
2334
2335         match header.constness {
2336             hir::Constness::NotConst => {}
2337             hir::Constness::Const => self.word_nbsp("const")?,
2338         }
2339
2340         match header.asyncness {
2341             hir::IsAsync::NotAsync => {}
2342             hir::IsAsync::Async => self.word_nbsp("async")?,
2343         }
2344
2345         self.print_unsafety(header.unsafety)?;
2346
2347         if header.abi != Abi::Rust {
2348             self.word_nbsp("extern")?;
2349             self.word_nbsp(&header.abi.to_string())?;
2350         }
2351
2352         self.s.word("fn")
2353     }
2354
2355     pub fn print_unsafety(&mut self, s: hir::Unsafety) -> io::Result<()> {
2356         match s {
2357             hir::Unsafety::Normal => Ok(()),
2358             hir::Unsafety::Unsafe => self.word_nbsp("unsafe"),
2359         }
2360     }
2361
2362     pub fn print_is_auto(&mut self, s: hir::IsAuto) -> io::Result<()> {
2363         match s {
2364             hir::IsAuto::Yes => self.word_nbsp("auto"),
2365             hir::IsAuto::No => Ok(()),
2366         }
2367     }
2368 }
2369
2370 // Dup'ed from parse::classify, but adapted for the HIR.
2371 /// Does this expression require a semicolon to be treated
2372 /// as a statement? The negation of this: 'can this expression
2373 /// be used as a statement without a semicolon' -- is used
2374 /// as an early-bail-out in the parser so that, for instance,
2375 ///     if true {...} else {...}
2376 ///      |x| 5
2377 /// isn't parsed as (if true {...} else {...} | x) | 5
2378 fn expr_requires_semi_to_be_stmt(e: &hir::Expr) -> bool {
2379     match e.node {
2380         hir::ExprKind::If(..) |
2381         hir::ExprKind::Match(..) |
2382         hir::ExprKind::Block(..) |
2383         hir::ExprKind::While(..) |
2384         hir::ExprKind::Loop(..) => false,
2385         _ => true,
2386     }
2387 }
2388
2389 /// this statement requires a semicolon after it.
2390 /// note that in one case (stmt_semi), we've already
2391 /// seen the semicolon, and thus don't need another.
2392 fn stmt_ends_with_semi(stmt: &hir::StmtKind) -> bool {
2393     match *stmt {
2394         hir::StmtKind::Decl(ref d, _) => {
2395             match d.node {
2396                 hir::DeclKind::Local(_) => true,
2397                 hir::DeclKind::Item(_) => false,
2398             }
2399         }
2400         hir::StmtKind::Expr(ref e, _) => {
2401             expr_requires_semi_to_be_stmt(&e)
2402         }
2403         hir::StmtKind::Semi(..) => {
2404             false
2405         }
2406     }
2407 }
2408
2409 fn bin_op_to_assoc_op(op: hir::BinOpKind) -> AssocOp {
2410     use hir::BinOpKind::*;
2411     match op {
2412         Add => AssocOp::Add,
2413         Sub => AssocOp::Subtract,
2414         Mul => AssocOp::Multiply,
2415         Div => AssocOp::Divide,
2416         Rem => AssocOp::Modulus,
2417
2418         And => AssocOp::LAnd,
2419         Or => AssocOp::LOr,
2420
2421         BitXor => AssocOp::BitXor,
2422         BitAnd => AssocOp::BitAnd,
2423         BitOr => AssocOp::BitOr,
2424         Shl => AssocOp::ShiftLeft,
2425         Shr => AssocOp::ShiftRight,
2426
2427         Eq => AssocOp::Equal,
2428         Lt => AssocOp::Less,
2429         Le => AssocOp::LessEqual,
2430         Ne => AssocOp::NotEqual,
2431         Ge => AssocOp::GreaterEqual,
2432         Gt => AssocOp::Greater,
2433     }
2434 }
2435
2436 /// Expressions that syntactically contain an "exterior" struct literal i.e. not surrounded by any
2437 /// parens or other delimiters, e.g. `X { y: 1 }`, `X { y: 1 }.method()`, `foo == X { y: 1 }` and
2438 /// `X { y: 1 } == foo` all do, but `(X { y: 1 }) == foo` does not.
2439 fn contains_exterior_struct_lit(value: &hir::Expr) -> bool {
2440     match value.node {
2441         hir::ExprKind::Struct(..) => true,
2442
2443         hir::ExprKind::Assign(ref lhs, ref rhs) |
2444         hir::ExprKind::AssignOp(_, ref lhs, ref rhs) |
2445         hir::ExprKind::Binary(_, ref lhs, ref rhs) => {
2446             // X { y: 1 } + X { y: 2 }
2447             contains_exterior_struct_lit(&lhs) || contains_exterior_struct_lit(&rhs)
2448         }
2449         hir::ExprKind::Unary(_, ref x) |
2450         hir::ExprKind::Cast(ref x, _) |
2451         hir::ExprKind::Type(ref x, _) |
2452         hir::ExprKind::Field(ref x, _) |
2453         hir::ExprKind::Index(ref x, _) => {
2454             // &X { y: 1 }, X { y: 1 }.y
2455             contains_exterior_struct_lit(&x)
2456         }
2457
2458         hir::ExprKind::MethodCall(.., ref exprs) => {
2459             // X { y: 1 }.bar(...)
2460             contains_exterior_struct_lit(&exprs[0])
2461         }
2462
2463         _ => false,
2464     }
2465 }