src/librustc/hir/print.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 pub use self::AnnNode::*;
  12
  13 use rustc_target::spec::abi::Abi;
  14 use syntax::ast;
  15 use syntax::codemap::{CodeMap, Spanned};
  16 use syntax::parse::ParseSess;
  17 use syntax::parse::lexer::comments;
  18 use syntax::print::pp::{self, Breaks};
  19 use syntax::print::pp::Breaks::{Consistent, Inconsistent};
  20 use syntax::print::pprust::PrintState;
  21 use syntax::ptr::P;
  22 use syntax::symbol::keywords;
  23 use syntax::util::parser::{self, AssocOp, Fixity};
  24 use syntax_pos::{self, BytePos, FileName};
  25
  26 use hir;
  27 use hir::{PatKind, GenericBound, TraitBoundModifier, RangeEnd};
  28 use hir::{GenericParam, GenericParamKind, GenericArg};
  29
  30 use std::cell::Cell;
  31 use std::io::{self, Write, Read};
  32 use std::iter::Peekable;
  33 use std::vec;
  34
  35 pub enum AnnNode<'a> {
  36     NodeName(&'a ast::Name),
  37     NodeBlock(&'a hir::Block),
  38     NodeItem(&'a hir::Item),
  39     NodeSubItem(ast::NodeId),
  40     NodeExpr(&'a hir::Expr),
  41     NodePat(&'a hir::Pat),
  42 }
  43
  44 pub enum Nested {
  45     Item(hir::ItemId),
  46     TraitItem(hir::TraitItemId),
  47     ImplItem(hir::ImplItemId),
  48     Body(hir::BodyId),
  49     BodyArgPat(hir::BodyId, usize)
  50 }
  51
  52 pub trait PpAnn {
  53     fn nested(&self, _state: &mut State, _nested: Nested) -> io::Result<()> {
  54         Ok(())
  55     }
  56     fn pre(&self, _state: &mut State, _node: AnnNode) -> io::Result<()> {
  57         Ok(())
  58     }
  59     fn post(&self, _state: &mut State, _node: AnnNode) -> io::Result<()> {
  60         Ok(())
  61     }
  62     fn try_fetch_item(&self, _: ast::NodeId) -> Option<&hir::Item> {
  63         None
  64     }
  65 }
  66
  67 pub struct NoAnn;
  68 impl PpAnn for NoAnn {}
  69 pub const NO_ANN: &'static dyn PpAnn = &NoAnn;
  70
  71 impl PpAnn for hir::Crate {
  72     fn try_fetch_item(&self, item: ast::NodeId) -> Option<&hir::Item> {
  73         Some(self.item(item))
  74     }
  75     fn nested(&self, state: &mut State, nested: Nested) -> io::Result<()> {
  76         match nested {
  77             Nested::Item(id) => state.print_item(self.item(id.id)),
  78             Nested::TraitItem(id) => state.print_trait_item(self.trait_item(id)),
  79             Nested::ImplItem(id) => state.print_impl_item(self.impl_item(id)),
  80             Nested::Body(id) => state.print_expr(&self.body(id).value),
  81             Nested::BodyArgPat(id, i) => state.print_pat(&self.body(id).arguments[i].pat)
  82         }
  83     }
  84 }
  85
  86 pub struct State<'a> {
  87     pub s: pp::Printer<'a>,
  88     cm: Option<&'a CodeMap>,
  89     comments: Option<Vec<comments::Comment>>,
  90     literals: Peekable<vec::IntoIter<comments::Literal>>,
  91     cur_cmnt: usize,
  92     boxes: Vec<pp::Breaks>,
  93     ann: &'a (dyn PpAnn + 'a),
  94 }
  95
  96 impl<'a> PrintState<'a> for State<'a> {
  97     fn writer(&mut self) -> &mut pp::Printer<'a> {
  98         &mut self.s
  99     }
 100
 101     fn boxes(&mut self) -> &mut Vec<pp::Breaks> {
 102         &mut self.boxes
 103     }
 104
 105     fn comments(&mut self) -> &mut Option<Vec<comments::Comment>> {
 106         &mut self.comments
 107     }
 108
 109     fn cur_cmnt(&mut self) -> &mut usize {
 110         &mut self.cur_cmnt
 111     }
 112
 113     fn cur_lit(&mut self) -> Option<&comments::Literal> {
 114         self.literals.peek()
 115     }
 116
 117     fn bump_lit(&mut self) -> Option<comments::Literal> {
 118         self.literals.next()
 119     }
 120 }
 121
 122 #[allow(non_upper_case_globals)]
 123 pub const indent_unit: usize = 4;
 124
 125 #[allow(non_upper_case_globals)]
 126 pub const default_columns: usize = 78;
 127
 128
 129 /// Requires you to pass an input filename and reader so that
 130 /// it can scan the input text for comments and literals to
 131 /// copy forward.
 132 pub fn print_crate<'a>(cm: &'a CodeMap,
 133                        sess: &ParseSess,
 134                        krate: &hir::Crate,
 135                        filename: FileName,
 136                        input: &mut dyn Read,
 137                        out: Box<dyn Write + 'a>,
 138                        ann: &'a dyn PpAnn,
 139                        is_expanded: bool)
 140                        -> io::Result<()> {
 141     let mut s = State::new_from_input(cm, sess, filename, input, out, ann, is_expanded);
 142
 143     // When printing the AST, we sometimes need to inject `#[no_std]` here.
 144     // Since you can't compile the HIR, it's not necessary.
 145
 146     s.print_mod(&krate.module, &krate.attrs)?;
 147     s.print_remaining_comments()?;
 148     s.s.eof()
 149 }
 150
 151 impl<'a> State<'a> {
 152     pub fn new_from_input(cm: &'a CodeMap,
 153                           sess: &ParseSess,
 154                           filename: FileName,
 155                           input: &mut dyn Read,
 156                           out: Box<dyn Write + 'a>,
 157                           ann: &'a dyn PpAnn,
 158                           is_expanded: bool)
 159                           -> State<'a> {
 160         let (cmnts, lits) = comments::gather_comments_and_literals(sess, filename, input);
 161
 162         State::new(cm,
 163                    out,
 164                    ann,
 165                    Some(cmnts),
 166                    // If the code is post expansion, don't use the table of
 167                    // literals, since it doesn't correspond with the literals
 168                    // in the AST anymore.
 169                    if is_expanded {
 170                        None
 171                    } else {
 172                        Some(lits)
 173                    })
 174     }
 175
 176     pub fn new(cm: &'a CodeMap,
 177                out: Box<dyn Write + 'a>,
 178                ann: &'a dyn PpAnn,
 179                comments: Option<Vec<comments::Comment>>,
 180                literals: Option<Vec<comments::Literal>>)
 181                -> State<'a> {
 182         State {
 183             s: pp::mk_printer(out, default_columns),
 184             cm: Some(cm),
 185             comments: comments.clone(),
 186             literals: literals.unwrap_or_default().into_iter().peekable(),
 187             cur_cmnt: 0,
 188             boxes: Vec::new(),
 189             ann,
 190         }
 191     }
 192 }
 193
 194 pub fn to_string<F>(ann: &dyn PpAnn, f: F) -> String
 195     where F: FnOnce(&mut State) -> io::Result<()>
 196 {
 197     let mut wr = Vec::new();
 198     {
 199         let mut printer = State {
 200             s: pp::mk_printer(Box::new(&mut wr), default_columns),
 201             cm: None,
 202             comments: None,
 203             literals: vec![].into_iter().peekable(),
 204             cur_cmnt: 0,
 205             boxes: Vec::new(),
 206             ann,
 207         };
 208         f(&mut printer).unwrap();
 209         printer.s.eof().unwrap();
 210     }
 211     String::from_utf8(wr).unwrap()
 212 }
 213
 214 pub fn visibility_qualified(vis: &hir::Visibility, w: &str) -> String {
 215     to_string(NO_ANN, |s| {
 216         s.print_visibility(vis)?;
 217         s.s.word(w)
 218     })
 219 }
 220
 221 impl<'a> State<'a> {
 222     pub fn cbox(&mut self, u: usize) -> io::Result<()> {
 223         self.boxes.push(pp::Breaks::Consistent);
 224         self.s.cbox(u)
 225     }
 226
 227     pub fn nbsp(&mut self) -> io::Result<()> {
 228         self.s.word(" ")
 229     }
 230
 231     pub fn word_nbsp(&mut self, w: &str) -> io::Result<()> {
 232         self.s.word(w)?;
 233         self.nbsp()
 234     }
 235
 236     pub fn head(&mut self, w: &str) -> io::Result<()> {
 237         // outer-box is consistent
 238         self.cbox(indent_unit)?;
 239         // head-box is inconsistent
 240         self.ibox(w.len() + 1)?;
 241         // keyword that starts the head
 242         if !w.is_empty() {
 243             self.word_nbsp(w)?;
 244         }
 245         Ok(())
 246     }
 247
 248     pub fn bopen(&mut self) -> io::Result<()> {
 249         self.s.word("{")?;
 250         self.end() // close the head-box
 251     }
 252
 253     pub fn bclose_(&mut self, span: syntax_pos::Span, indented: usize) -> io::Result<()> {
 254         self.bclose_maybe_open(span, indented, true)
 255     }
 256     pub fn bclose_maybe_open(&mut self,
 257                              span: syntax_pos::Span,
 258                              indented: usize,
 259                              close_box: bool)
 260                              -> io::Result<()> {
 261         self.maybe_print_comment(span.hi())?;
 262         self.break_offset_if_not_bol(1, -(indented as isize))?;
 263         self.s.word("}")?;
 264         if close_box {
 265             self.end()?; // close the outer-box
 266         }
 267         Ok(())
 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     pub fn space_if_not_bol(&mut self) -> io::Result<()> {
 280         if !self.is_bol() {
 281             self.s.space()?;
 282         }
 283         Ok(())
 284     }
 285     pub fn break_offset_if_not_bol(&mut self, n: usize, off: isize) -> io::Result<()> {
 286         if !self.is_bol() {
 287             self.s.break_offset(n, off)
 288         } else {
 289             if off != 0 && self.s.last_token().is_hardbreak_tok() {
 290                 // We do something pretty sketchy here: tuck the nonzero
 291                 // offset-adjustment we were going to deposit along with the
 292                 // break into the previous hardbreak.
 293                 self.s.replace_last_token(pp::Printer::hardbreak_tok_offset(off));
 294             }
 295             Ok(())
 296         }
 297     }
 298
 299     // Synthesizes a comment that was not textually present in the original source
 300     // file.
 301     pub fn synth_comment(&mut self, text: String) -> io::Result<()> {
 302         self.s.word("/*")?;
 303         self.s.space()?;
 304         self.s.word(&text[..])?;
 305         self.s.space()?;
 306         self.s.word("*/")
 307     }
 308
 309
 310     pub fn commasep_cmnt<T, F, G>(&mut self,
 311                                   b: Breaks,
 312                                   elts: &[T],
 313                                   mut op: F,
 314                                   mut get_span: G)
 315                                   -> io::Result<()>
 316         where F: FnMut(&mut State, &T) -> io::Result<()>,
 317               G: FnMut(&T) -> syntax_pos::Span
 318     {
 319         self.rbox(0, b)?;
 320         let len = elts.len();
 321         let mut i = 0;
 322         for elt in elts {
 323             self.maybe_print_comment(get_span(elt).hi())?;
 324             op(self, elt)?;
 325             i += 1;
 326             if i < len {
 327                 self.s.word(",")?;
 328                 self.maybe_print_trailing_comment(get_span(elt), Some(get_span(&elts[i]).hi()))?;
 329                 self.space_if_not_bol()?;
 330             }
 331         }
 332         self.end()
 333     }
 334
 335     pub fn commasep_exprs(&mut self, b: Breaks, exprs: &[hir::Expr]) -> io::Result<()> {
 336         self.commasep_cmnt(b, exprs, |s, e| s.print_expr(&e), |e| e.span)
 337     }
 338
 339     pub fn print_mod(&mut self, _mod: &hir::Mod, attrs: &[ast::Attribute]) -> io::Result<()> {
 340         self.print_inner_attributes(attrs)?;
 341         for &item_id in &_mod.item_ids {
 342             self.ann.nested(self, Nested::Item(item_id))?;
 343         }
 344         Ok(())
 345     }
 346
 347     pub fn print_foreign_mod(&mut self,
 348                              nmod: &hir::ForeignMod,
 349                              attrs: &[ast::Attribute])
 350                              -> io::Result<()> {
 351         self.print_inner_attributes(attrs)?;
 352         for item in &nmod.items {
 353             self.print_foreign_item(item)?;
 354         }
 355         Ok(())
 356     }
 357
 358     pub fn print_opt_lifetime(&mut self, lifetime: &hir::Lifetime) -> io::Result<()> {
 359         if !lifetime.is_elided() {
 360             self.print_lifetime(lifetime)?;
 361             self.nbsp()?;
 362         }
 363         Ok(())
 364     }
 365
 366     pub fn print_type(&mut self, ty: &hir::Ty) -> io::Result<()> {
 367         self.maybe_print_comment(ty.span.lo())?;
 368         self.ibox(0)?;
 369         match ty.node {
 370             hir::TySlice(ref ty) => {
 371                 self.s.word("[")?;
 372                 self.print_type(&ty)?;
 373                 self.s.word("]")?;
 374             }
 375             hir::TyPtr(ref mt) => {
 376                 self.s.word("*")?;
 377                 match mt.mutbl {
 378                     hir::MutMutable => self.word_nbsp("mut")?,
 379                     hir::MutImmutable => self.word_nbsp("const")?,
 380                 }
 381                 self.print_type(&mt.ty)?;
 382             }
 383             hir::TyRptr(ref lifetime, ref mt) => {
 384                 self.s.word("&")?;
 385                 self.print_opt_lifetime(lifetime)?;
 386                 self.print_mt(mt)?;
 387             }
 388             hir::TyNever => {
 389                 self.s.word("!")?;
 390             },
 391             hir::TyTup(ref elts) => {
 392                 self.popen()?;
 393                 self.commasep(Inconsistent, &elts[..], |s, ty| s.print_type(&ty))?;
 394                 if elts.len() == 1 {
 395                     self.s.word(",")?;
 396                 }
 397                 self.pclose()?;
 398             }
 399             hir::TyBareFn(ref f) => {
 400                 self.print_ty_fn(f.abi, f.unsafety, &f.decl, None, &f.generic_params,
 401                                  &f.arg_names[..])?;
 402             }
 403             hir::TyPath(ref qpath) => {
 404                 self.print_qpath(qpath, false)?
 405             }
 406             hir::TyTraitObject(ref bounds, ref lifetime) => {
 407                 let mut first = true;
 408                 for bound in bounds {
 409                     if first {
 410                         first = false;
 411                     } else {
 412                         self.nbsp()?;
 413                         self.word_space("+")?;
 414                     }
 415                     self.print_poly_trait_ref(bound)?;
 416                 }
 417                 if !lifetime.is_elided() {
 418                     self.nbsp()?;
 419                     self.word_space("+")?;
 420                     self.print_lifetime(lifetime)?;
 421                 }
 422             }
 423             hir::TyImplTraitExistential(hir_id, _def_id, ref _lifetimes) => {
 424                 match self.ann.try_fetch_item(hir_id.id).map(|it| &it.node) {
 425                     None => self.word_space("impl {{Trait}}")?,
 426                     Some(&hir::ItemExistential(ref exist_ty)) => {
 427                         self.print_bounds("impl", &exist_ty.bounds)?;
 428                     },
 429                     other => bug!("impl Trait pointed to {:#?}", other),
 430                 }
 431             }
 432             hir::TyArray(ref ty, ref length) => {
 433                 self.s.word("[")?;
 434                 self.print_type(&ty)?;
 435                 self.s.word("; ")?;
 436                 self.print_anon_const(length)?;
 437                 self.s.word("]")?;
 438             }
 439             hir::TyTypeof(ref e) => {
 440                 self.s.word("typeof(")?;
 441                 self.print_anon_const(e)?;
 442                 self.s.word(")")?;
 443             }
 444             hir::TyInfer => {
 445                 self.s.word("_")?;
 446             }
 447             hir::TyErr => {
 448                 self.s.word("?")?;
 449             }
 450         }
 451         self.end()
 452     }
 453
 454     pub fn print_foreign_item(&mut self, item: &hir::ForeignItem) -> io::Result<()> {
 455         self.hardbreak_if_not_bol()?;
 456         self.maybe_print_comment(item.span.lo())?;
 457         self.print_outer_attributes(&item.attrs)?;
 458         match item.node {
 459             hir::ForeignItemFn(ref decl, ref arg_names, ref generics) => {
 460                 self.head("")?;
 461                 self.print_fn(decl,
 462                               hir::FnHeader {
 463                                   unsafety: hir::Unsafety::Normal,
 464                                   constness: hir::Constness::NotConst,
 465                                   abi: Abi::Rust,
 466                                   asyncness: hir::IsAsync::NotAsync,
 467                               },
 468                               Some(item.name),
 469                               generics,
 470                               &item.vis,
 471                               arg_names,
 472                               None)?;
 473                 self.end()?; // end head-ibox
 474                 self.s.word(";")?;
 475                 self.end() // end the outer fn box
 476             }
 477             hir::ForeignItemStatic(ref t, m) => {
 478                 self.head(&visibility_qualified(&item.vis, "static"))?;
 479                 if m {
 480                     self.word_space("mut")?;
 481                 }
 482                 self.print_name(item.name)?;
 483                 self.word_space(":")?;
 484                 self.print_type(&t)?;
 485                 self.s.word(";")?;
 486                 self.end()?; // end the head-ibox
 487                 self.end() // end the outer cbox
 488             }
 489             hir::ForeignItemType => {
 490                 self.head(&visibility_qualified(&item.vis, "type"))?;
 491                 self.print_name(item.name)?;
 492                 self.s.word(";")?;
 493                 self.end()?; // end the head-ibox
 494                 self.end() // end the outer cbox
 495             }
 496         }
 497     }
 498
 499     fn print_associated_const(&mut self,
 500                               ident: ast::Ident,
 501                               ty: &hir::Ty,
 502                               default: Option<hir::BodyId>,
 503                               vis: &hir::Visibility)
 504                               -> io::Result<()> {
 505         self.s.word(&visibility_qualified(vis, ""))?;
 506         self.word_space("const")?;
 507         self.print_ident(ident)?;
 508         self.word_space(":")?;
 509         self.print_type(ty)?;
 510         if let Some(expr) = default {
 511             self.s.space()?;
 512             self.word_space("=")?;
 513             self.ann.nested(self, Nested::Body(expr))?;
 514         }
 515         self.s.word(";")
 516     }
 517
 518     fn print_associated_type(&mut self,
 519                              ident: ast::Ident,
 520                              bounds: Option<&hir::GenericBounds>,
 521                              ty: Option<&hir::Ty>)
 522                              -> io::Result<()> {
 523         self.word_space("type")?;
 524         self.print_ident(ident)?;
 525         if let Some(bounds) = bounds {
 526             self.print_bounds(":", bounds)?;
 527         }
 528         if let Some(ty) = ty {
 529             self.s.space()?;
 530             self.word_space("=")?;
 531             self.print_type(ty)?;
 532         }
 533         self.s.word(";")
 534     }
 535
 536     /// Pretty-print an item
 537     pub fn print_item(&mut self, item: &hir::Item) -> io::Result<()> {
 538         self.hardbreak_if_not_bol()?;
 539         self.maybe_print_comment(item.span.lo())?;
 540         self.print_outer_attributes(&item.attrs)?;
 541         self.ann.pre(self, NodeItem(item))?;
 542         match item.node {
 543             hir::ItemExternCrate(orig_name) => {
 544                 self.head(&visibility_qualified(&item.vis, "extern crate"))?;
 545                 if let Some(orig_name) = orig_name {
 546                     self.print_name(orig_name)?;
 547                     self.s.space()?;
 548                     self.s.word("as")?;
 549                     self.s.space()?;
 550                 }
 551                 self.print_name(item.name)?;
 552                 self.s.word(";")?;
 553                 self.end()?; // end inner head-block
 554                 self.end()?; // end outer head-block
 555             }
 556             hir::ItemUse(ref path, kind) => {
 557                 self.head(&visibility_qualified(&item.vis, "use"))?;
 558                 self.print_path(path, false)?;
 559
 560                 match kind {
 561                     hir::UseKind::Single => {
 562                         if path.segments.last().unwrap().ident.name != item.name {
 563                             self.s.space()?;
 564                             self.word_space("as")?;
 565                             self.print_name(item.name)?;
 566                         }
 567                         self.s.word(";")?;
 568                     }
 569                     hir::UseKind::Glob => self.s.word("::*;")?,
 570                     hir::UseKind::ListStem => self.s.word("::{};")?
 571                 }
 572                 self.end()?; // end inner head-block
 573                 self.end()?; // end outer head-block
 574             }
 575             hir::ItemStatic(ref ty, m, expr) => {
 576                 self.head(&visibility_qualified(&item.vis, "static"))?;
 577                 if m == hir::MutMutable {
 578                     self.word_space("mut")?;
 579                 }
 580                 self.print_name(item.name)?;
 581                 self.word_space(":")?;
 582                 self.print_type(&ty)?;
 583                 self.s.space()?;
 584                 self.end()?; // end the head-ibox
 585
 586                 self.word_space("=")?;
 587                 self.ann.nested(self, Nested::Body(expr))?;
 588                 self.s.word(";")?;
 589                 self.end()?; // end the outer cbox
 590             }
 591             hir::ItemConst(ref ty, expr) => {
 592                 self.head(&visibility_qualified(&item.vis, "const"))?;
 593                 self.print_name(item.name)?;
 594                 self.word_space(":")?;
 595                 self.print_type(&ty)?;
 596                 self.s.space()?;
 597                 self.end()?; // end the head-ibox
 598
 599                 self.word_space("=")?;
 600                 self.ann.nested(self, Nested::Body(expr))?;
 601                 self.s.word(";")?;
 602                 self.end()?; // end the outer cbox
 603             }
 604             hir::ItemFn(ref decl, header, ref typarams, body) => {
 605                 self.head("")?;
 606                 self.print_fn(decl,
 607                               header,
 608                               Some(item.name),
 609                               typarams,
 610                               &item.vis,
 611                               &[],
 612                               Some(body))?;
 613                 self.s.word(" ")?;
 614                 self.end()?; // need to close a box
 615                 self.end()?; // need to close a box
 616                 self.ann.nested(self, Nested::Body(body))?;
 617             }
 618             hir::ItemMod(ref _mod) => {
 619                 self.head(&visibility_qualified(&item.vis, "mod"))?;
 620                 self.print_name(item.name)?;
 621                 self.nbsp()?;
 622                 self.bopen()?;
 623                 self.print_mod(_mod, &item.attrs)?;
 624                 self.bclose(item.span)?;
 625             }
 626             hir::ItemForeignMod(ref nmod) => {
 627                 self.head("extern")?;
 628                 self.word_nbsp(&nmod.abi.to_string())?;
 629                 self.bopen()?;
 630                 self.print_foreign_mod(nmod, &item.attrs)?;
 631                 self.bclose(item.span)?;
 632             }
 633             hir::ItemGlobalAsm(ref ga) => {
 634                 self.head(&visibility_qualified(&item.vis, "global asm"))?;
 635                 self.s.word(&ga.asm.as_str())?;
 636                 self.end()?
 637             }
 638             hir::ItemTy(ref ty, ref generics) => {
 639                 self.ibox(indent_unit)?;
 640                 self.ibox(0)?;
 641                 self.word_nbsp(&visibility_qualified(&item.vis, "type"))?;
 642                 self.print_name(item.name)?;
 643                 self.print_generic_params(&generics.params)?;
 644                 self.end()?; // end the inner ibox
 645
 646                 self.print_where_clause(&generics.where_clause)?;
 647                 self.s.space()?;
 648                 self.word_space("=")?;
 649                 self.print_type(&ty)?;
 650                 self.s.word(";")?;
 651                 self.end()?; // end the outer ibox
 652             }
 653             hir::ItemExistential(ref exist) => {
 654                 self.ibox(indent_unit)?;
 655                 self.ibox(0)?;
 656                 self.word_nbsp(&visibility_qualified(&item.vis, "existential type"))?;
 657                 self.print_name(item.name)?;
 658                 self.print_generic_params(&exist.generics.params)?;
 659                 self.end()?; // end the inner ibox
 660
 661                 self.print_where_clause(&exist.generics.where_clause)?;
 662                 self.s.space()?;
 663                 self.word_space(":")?;
 664                 let mut real_bounds = Vec::with_capacity(exist.bounds.len());
 665                 for b in exist.bounds.iter() {
 666                     if let GenericBound::Trait(ref ptr, hir::TraitBoundModifier::Maybe) = *b {
 667                         self.s.space()?;
 668                         self.word_space("for ?")?;
 669                         self.print_trait_ref(&ptr.trait_ref)?;
 670                     } else {
 671                         real_bounds.push(b.clone());
 672                     }
 673                 }
 674                 self.print_bounds(":", &real_bounds[..])?;
 675                 self.s.word(";")?;
 676                 self.end()?; // end the outer ibox
 677             }
 678             hir::ItemEnum(ref enum_definition, ref params) => {
 679                 self.print_enum_def(enum_definition, params, item.name, item.span, &item.vis)?;
 680             }
 681             hir::ItemStruct(ref struct_def, ref generics) => {
 682                 self.head(&visibility_qualified(&item.vis, "struct"))?;
 683                 self.print_struct(struct_def, generics, item.name, item.span, true)?;
 684             }
 685             hir::ItemUnion(ref struct_def, ref generics) => {
 686                 self.head(&visibility_qualified(&item.vis, "union"))?;
 687                 self.print_struct(struct_def, generics, item.name, item.span, true)?;
 688             }
 689             hir::ItemImpl(unsafety,
 690                           polarity,
 691                           defaultness,
 692                           ref generics,
 693                           ref opt_trait,
 694                           ref ty,
 695                           ref impl_items) => {
 696                 self.head("")?;
 697                 self.print_visibility(&item.vis)?;
 698                 self.print_defaultness(defaultness)?;
 699                 self.print_unsafety(unsafety)?;
 700                 self.word_nbsp("impl")?;
 701
 702                 if !generics.params.is_empty() {
 703                     self.print_generic_params(&generics.params)?;
 704                     self.s.space()?;
 705                 }
 706
 707                 match polarity {
 708                     hir::ImplPolarity::Negative => {
 709                         self.s.word("!")?;
 710                     }
 711                     _ => {}
 712                 }
 713
 714                 match opt_trait {
 715                     &Some(ref t) => {
 716                         self.print_trait_ref(t)?;
 717                         self.s.space()?;
 718                         self.word_space("for")?;
 719                     }
 720                     &None => {}
 721                 }
 722
 723                 self.print_type(&ty)?;
 724                 self.print_where_clause(&generics.where_clause)?;
 725
 726                 self.s.space()?;
 727                 self.bopen()?;
 728                 self.print_inner_attributes(&item.attrs)?;
 729                 for impl_item in impl_items {
 730                     self.ann.nested(self, Nested::ImplItem(impl_item.id))?;
 731                 }
 732                 self.bclose(item.span)?;
 733             }
 734             hir::ItemTrait(is_auto, unsafety, ref generics, ref bounds, ref trait_items) => {
 735                 self.head("")?;
 736                 self.print_visibility(&item.vis)?;
 737                 self.print_is_auto(is_auto)?;
 738                 self.print_unsafety(unsafety)?;
 739                 self.word_nbsp("trait")?;
 740                 self.print_name(item.name)?;
 741                 self.print_generic_params(&generics.params)?;
 742                 let mut real_bounds = Vec::with_capacity(bounds.len());
 743                 for b in bounds.iter() {
 744                     if let GenericBound::Trait(ref ptr, hir::TraitBoundModifier::Maybe) = *b {
 745                         self.s.space()?;
 746                         self.word_space("for ?")?;
 747                         self.print_trait_ref(&ptr.trait_ref)?;
 748                     } else {
 749                         real_bounds.push(b.clone());
 750                     }
 751                 }
 752                 self.print_bounds(":", &real_bounds[..])?;
 753                 self.print_where_clause(&generics.where_clause)?;
 754                 self.s.word(" ")?;
 755                 self.bopen()?;
 756                 for trait_item in trait_items {
 757                     self.ann.nested(self, Nested::TraitItem(trait_item.id))?;
 758                 }
 759                 self.bclose(item.span)?;
 760             }
 761             hir::ItemTraitAlias(ref generics, ref bounds) => {
 762                 self.head("")?;
 763                 self.print_visibility(&item.vis)?;
 764                 self.word_nbsp("trait")?;
 765                 self.print_name(item.name)?;
 766                 self.print_generic_params(&generics.params)?;
 767                 let mut real_bounds = Vec::with_capacity(bounds.len());
 768                 // FIXME(durka) this seems to be some quite outdated syntax
 769                 for b in bounds.iter() {
 770                     if let GenericBound::Trait(ref ptr, hir::TraitBoundModifier::Maybe) = *b {
 771                         self.s.space()?;
 772                         self.word_space("for ?")?;
 773                         self.print_trait_ref(&ptr.trait_ref)?;
 774                     } else {
 775                         real_bounds.push(b.clone());
 776                     }
 777                 }
 778                 self.nbsp()?;
 779                 self.print_bounds("=", &real_bounds[..])?;
 780                 self.print_where_clause(&generics.where_clause)?;
 781                 self.s.word(";")?;
 782             }
 783         }
 784         self.ann.post(self, NodeItem(item))
 785     }
 786
 787     pub fn print_trait_ref(&mut self, t: &hir::TraitRef) -> io::Result<()> {
 788         self.print_path(&t.path, false)
 789     }
 790
 791     fn print_formal_generic_params(
 792         &mut self,
 793         generic_params: &[hir::GenericParam]
 794     ) -> io::Result<()> {
 795         if !generic_params.is_empty() {
 796             self.s.word("for")?;
 797             self.print_generic_params(generic_params)?;
 798             self.nbsp()?;
 799         }
 800         Ok(())
 801     }
 802
 803     fn print_poly_trait_ref(&mut self, t: &hir::PolyTraitRef) -> io::Result<()> {
 804         self.print_formal_generic_params(&t.bound_generic_params)?;
 805         self.print_trait_ref(&t.trait_ref)
 806     }
 807
 808     pub fn print_enum_def(&mut self,
 809                           enum_definition: &hir::EnumDef,
 810                           generics: &hir::Generics,
 811                           name: ast::Name,
 812                           span: syntax_pos::Span,
 813                           visibility: &hir::Visibility)
 814                           -> io::Result<()> {
 815         self.head(&visibility_qualified(visibility, "enum"))?;
 816         self.print_name(name)?;
 817         self.print_generic_params(&generics.params)?;
 818         self.print_where_clause(&generics.where_clause)?;
 819         self.s.space()?;
 820         self.print_variants(&enum_definition.variants, span)
 821     }
 822
 823     pub fn print_variants(&mut self,
 824                           variants: &[hir::Variant],
 825                           span: syntax_pos::Span)
 826                           -> io::Result<()> {
 827         self.bopen()?;
 828         for v in variants {
 829             self.space_if_not_bol()?;
 830             self.maybe_print_comment(v.span.lo())?;
 831             self.print_outer_attributes(&v.node.attrs)?;
 832             self.ibox(indent_unit)?;
 833             self.print_variant(v)?;
 834             self.s.word(",")?;
 835             self.end()?;
 836             self.maybe_print_trailing_comment(v.span, None)?;
 837         }
 838         self.bclose(span)
 839     }
 840
 841     pub fn print_visibility(&mut self, vis: &hir::Visibility) -> io::Result<()> {
 842         match vis.node {
 843             hir::VisibilityKind::Public => self.word_nbsp("pub")?,
 844             hir::VisibilityKind::Crate(ast::CrateSugar::JustCrate) => self.word_nbsp("crate")?,
 845             hir::VisibilityKind::Crate(ast::CrateSugar::PubCrate) => self.word_nbsp("pub(crate)")?,
 846             hir::VisibilityKind::Restricted { ref path, .. } => {
 847                 self.s.word("pub(")?;
 848                 if path.segments.len() == 1 &&
 849                    path.segments[0].ident.name == keywords::Super.name() {
 850                     // Special case: `super` can print like `pub(super)`.
 851                     self.s.word("super")?;
 852                 } else {
 853                     // Everything else requires `in` at present.
 854                     self.word_nbsp("in")?;
 855                     self.print_path(path, false)?;
 856                 }
 857                 self.word_nbsp(")")?;
 858             }
 859             hir::VisibilityKind::Inherited => ()
 860         }
 861
 862         Ok(())
 863     }
 864
 865     pub fn print_defaultness(&mut self, defaultness: hir::Defaultness) -> io::Result<()> {
 866         match defaultness {
 867             hir::Defaultness::Default { .. } => self.word_nbsp("default")?,
 868             hir::Defaultness::Final => (),
 869         }
 870         Ok(())
 871     }
 872
 873     pub fn print_struct(&mut self,
 874                         struct_def: &hir::VariantData,
 875                         generics: &hir::Generics,
 876                         name: ast::Name,
 877                         span: syntax_pos::Span,
 878                         print_finalizer: bool)
 879                         -> io::Result<()> {
 880         self.print_name(name)?;
 881         self.print_generic_params(&generics.params)?;
 882         if !struct_def.is_struct() {
 883             if struct_def.is_tuple() {
 884                 self.popen()?;
 885                 self.commasep(Inconsistent, struct_def.fields(), |s, field| {
 886                     s.maybe_print_comment(field.span.lo())?;
 887                     s.print_outer_attributes(&field.attrs)?;
 888                     s.print_visibility(&field.vis)?;
 889                     s.print_type(&field.ty)
 890                 })?;
 891                 self.pclose()?;
 892             }
 893             self.print_where_clause(&generics.where_clause)?;
 894             if print_finalizer {
 895                 self.s.word(";")?;
 896             }
 897             self.end()?;
 898             self.end() // close the outer-box
 899         } else {
 900             self.print_where_clause(&generics.where_clause)?;
 901             self.nbsp()?;
 902             self.bopen()?;
 903             self.hardbreak_if_not_bol()?;
 904
 905             for field in struct_def.fields() {
 906                 self.hardbreak_if_not_bol()?;
 907                 self.maybe_print_comment(field.span.lo())?;
 908                 self.print_outer_attributes(&field.attrs)?;
 909                 self.print_visibility(&field.vis)?;
 910                 self.print_ident(field.ident)?;
 911                 self.word_nbsp(":")?;
 912                 self.print_type(&field.ty)?;
 913                 self.s.word(",")?;
 914             }
 915
 916             self.bclose(span)
 917         }
 918     }
 919
 920     pub fn print_variant(&mut self, v: &hir::Variant) -> io::Result<()> {
 921         self.head("")?;
 922         let generics = hir::Generics::empty();
 923         self.print_struct(&v.node.data, &generics, v.node.name, v.span, false)?;
 924         if let Some(ref d) = v.node.disr_expr {
 925             self.s.space()?;
 926             self.word_space("=")?;
 927             self.print_anon_const(d)?;
 928         }
 929         Ok(())
 930     }
 931     pub fn print_method_sig(&mut self,
 932                             ident: ast::Ident,
 933                             m: &hir::MethodSig,
 934                             generics: &hir::Generics,
 935                             vis: &hir::Visibility,
 936                             arg_names: &[ast::Ident],
 937                             body_id: Option<hir::BodyId>)
 938                             -> io::Result<()> {
 939         self.print_fn(&m.decl,
 940                       m.header,
 941                       Some(ident.name),
 942                       generics,
 943                       vis,
 944                       arg_names,
 945                       body_id)
 946     }
 947
 948     pub fn print_trait_item(&mut self, ti: &hir::TraitItem) -> io::Result<()> {
 949         self.ann.pre(self, NodeSubItem(ti.id))?;
 950         self.hardbreak_if_not_bol()?;
 951         self.maybe_print_comment(ti.span.lo())?;
 952         self.print_outer_attributes(&ti.attrs)?;
 953         match ti.node {
 954             hir::TraitItemKind::Const(ref ty, default) => {
 955                 let vis = Spanned { span: syntax_pos::DUMMY_SP,
 956                                     node: hir::VisibilityKind::Inherited };
 957                 self.print_associated_const(ti.ident, &ty, default, &vis)?;
 958             }
 959             hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Required(ref arg_names)) => {
 960                 let vis = Spanned { span: syntax_pos::DUMMY_SP,
 961                                     node: hir::VisibilityKind::Inherited };
 962                 self.print_method_sig(ti.ident, sig, &ti.generics, &vis, arg_names, None)?;
 963                 self.s.word(";")?;
 964             }
 965             hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Provided(body)) => {
 966                 let vis = Spanned { span: syntax_pos::DUMMY_SP,
 967                                     node: hir::VisibilityKind::Inherited };
 968                 self.head("")?;
 969                 self.print_method_sig(ti.ident, sig, &ti.generics, &vis, &[], Some(body))?;
 970                 self.nbsp()?;
 971                 self.end()?; // need to close a box
 972                 self.end()?; // need to close a box
 973                 self.ann.nested(self, Nested::Body(body))?;
 974             }
 975             hir::TraitItemKind::Type(ref bounds, ref default) => {
 976                 self.print_associated_type(ti.ident,
 977                                            Some(bounds),
 978                                            default.as_ref().map(|ty| &**ty))?;
 979             }
 980         }
 981         self.ann.post(self, NodeSubItem(ti.id))
 982     }
 983
 984     pub fn print_impl_item(&mut self, ii: &hir::ImplItem) -> io::Result<()> {
 985         self.ann.pre(self, NodeSubItem(ii.id))?;
 986         self.hardbreak_if_not_bol()?;
 987         self.maybe_print_comment(ii.span.lo())?;
 988         self.print_outer_attributes(&ii.attrs)?;
 989         self.print_defaultness(ii.defaultness)?;
 990
 991         match ii.node {
 992             hir::ImplItemKind::Const(ref ty, expr) => {
 993                 self.print_associated_const(ii.ident, &ty, Some(expr), &ii.vis)?;
 994             }
 995             hir::ImplItemKind::Method(ref sig, body) => {
 996                 self.head("")?;
 997                 self.print_method_sig(ii.ident, sig, &ii.generics, &ii.vis, &[], Some(body))?;
 998                 self.nbsp()?;
 999                 self.end()?; // need to close a box
1000                 self.end()?; // need to close a box
1001                 self.ann.nested(self, Nested::Body(body))?;
1002             }
1003             hir::ImplItemKind::Type(ref ty) => {
1004                 self.print_associated_type(ii.ident, None, Some(ty))?;
1005             }
1006         }
1007         self.ann.post(self, NodeSubItem(ii.id))
1008     }
1009
1010     pub fn print_stmt(&mut self, st: &hir::Stmt) -> io::Result<()> {
1011         self.maybe_print_comment(st.span.lo())?;
1012         match st.node {
1013             hir::StmtDecl(ref decl, _) => {
1014                 self.print_decl(&decl)?;
1015             }
1016             hir::StmtExpr(ref expr, _) => {
1017                 self.space_if_not_bol()?;
1018                 self.print_expr(&expr)?;
1019             }
1020             hir::StmtSemi(ref expr, _) => {
1021                 self.space_if_not_bol()?;
1022                 self.print_expr(&expr)?;
1023                 self.s.word(";")?;
1024             }
1025         }
1026         if stmt_ends_with_semi(&st.node) {
1027             self.s.word(";")?;
1028         }
1029         self.maybe_print_trailing_comment(st.span, None)
1030     }
1031
1032     pub fn print_block(&mut self, blk: &hir::Block) -> io::Result<()> {
1033         self.print_block_with_attrs(blk, &[])
1034     }
1035
1036     pub fn print_block_unclosed(&mut self, blk: &hir::Block) -> io::Result<()> {
1037         self.print_block_unclosed_indent(blk, indent_unit)
1038     }
1039
1040     pub fn print_block_unclosed_indent(&mut self,
1041                                        blk: &hir::Block,
1042                                        indented: usize)
1043                                        -> io::Result<()> {
1044         self.print_block_maybe_unclosed(blk, indented, &[], false)
1045     }
1046
1047     pub fn print_block_with_attrs(&mut self,
1048                                   blk: &hir::Block,
1049                                   attrs: &[ast::Attribute])
1050                                   -> io::Result<()> {
1051         self.print_block_maybe_unclosed(blk, indent_unit, attrs, true)
1052     }
1053
1054     pub fn print_block_maybe_unclosed(&mut self,
1055                                       blk: &hir::Block,
1056                                       indented: usize,
1057                                       attrs: &[ast::Attribute],
1058                                       close_box: bool)
1059                                       -> io::Result<()> {
1060         match blk.rules {
1061             hir::UnsafeBlock(..) => self.word_space("unsafe")?,
1062             hir::PushUnsafeBlock(..) => self.word_space("push_unsafe")?,
1063             hir::PopUnsafeBlock(..) => self.word_space("pop_unsafe")?,
1064             hir::DefaultBlock => (),
1065         }
1066         self.maybe_print_comment(blk.span.lo())?;
1067         self.ann.pre(self, NodeBlock(blk))?;
1068         self.bopen()?;
1069
1070         self.print_inner_attributes(attrs)?;
1071
1072         for st in &blk.stmts {
1073             self.print_stmt(st)?;
1074         }
1075         match blk.expr {
1076             Some(ref expr) => {
1077                 self.space_if_not_bol()?;
1078                 self.print_expr(&expr)?;
1079                 self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi()))?;
1080             }
1081             _ => (),
1082         }
1083         self.bclose_maybe_open(blk.span, indented, close_box)?;
1084         self.ann.post(self, NodeBlock(blk))
1085     }
1086
1087     fn print_else(&mut self, els: Option<&hir::Expr>) -> io::Result<()> {
1088         match els {
1089             Some(_else) => {
1090                 match _else.node {
1091                     // "another else-if"
1092                     hir::ExprIf(ref i, ref then, ref e) => {
1093                         self.cbox(indent_unit - 1)?;
1094                         self.ibox(0)?;
1095                         self.s.word(" else if ")?;
1096                         self.print_expr_as_cond(&i)?;
1097                         self.s.space()?;
1098                         self.print_expr(&then)?;
1099                         self.print_else(e.as_ref().map(|e| &**e))
1100                     }
1101                     // "final else"
1102                     hir::ExprBlock(ref b, _) => {
1103                         self.cbox(indent_unit - 1)?;
1104                         self.ibox(0)?;
1105                         self.s.word(" else ")?;
1106                         self.print_block(&b)
1107                     }
1108                     // BLEAH, constraints would be great here
1109                     _ => {
1110                         panic!("print_if saw if with weird alternative");
1111                     }
1112                 }
1113             }
1114             _ => Ok(()),
1115         }
1116     }
1117
1118     pub fn print_if(&mut self,
1119                     test: &hir::Expr,
1120                     blk: &hir::Expr,
1121                     elseopt: Option<&hir::Expr>)
1122                     -> io::Result<()> {
1123         self.head("if")?;
1124         self.print_expr_as_cond(test)?;
1125         self.s.space()?;
1126         self.print_expr(blk)?;
1127         self.print_else(elseopt)
1128     }
1129
1130     pub fn print_if_let(&mut self,
1131                         pat: &hir::Pat,
1132                         expr: &hir::Expr,
1133                         blk: &hir::Block,
1134                         elseopt: Option<&hir::Expr>)
1135                         -> io::Result<()> {
1136         self.head("if let")?;
1137         self.print_pat(pat)?;
1138         self.s.space()?;
1139         self.word_space("=")?;
1140         self.print_expr_as_cond(expr)?;
1141         self.s.space()?;
1142         self.print_block(blk)?;
1143         self.print_else(elseopt)
1144     }
1145
1146     pub fn print_anon_const(&mut self, constant: &hir::AnonConst) -> io::Result<()> {
1147         self.ann.nested(self, Nested::Body(constant.body))
1148     }
1149
1150     fn print_call_post(&mut self, args: &[hir::Expr]) -> io::Result<()> {
1151         self.popen()?;
1152         self.commasep_exprs(Inconsistent, args)?;
1153         self.pclose()
1154     }
1155
1156     pub fn print_expr_maybe_paren(&mut self, expr: &hir::Expr, prec: i8) -> io::Result<()> {
1157         let needs_par = expr.precedence().order() < prec;
1158         if needs_par {
1159             self.popen()?;
1160         }
1161         self.print_expr(expr)?;
1162         if needs_par {
1163             self.pclose()?;
1164         }
1165         Ok(())
1166     }
1167
1168     /// Print an expr using syntax that's acceptable in a condition position, such as the `cond` in
1169     /// `if cond { ... }`.
1170     pub fn print_expr_as_cond(&mut self, expr: &hir::Expr) -> io::Result<()> {
1171         let needs_par = match expr.node {
1172             // These cases need parens due to the parse error observed in #26461: `if return {}`
1173             // parses as the erroneous construct `if (return {})`, not `if (return) {}`.
1174             hir::ExprClosure(..) |
1175             hir::ExprRet(..) |
1176             hir::ExprBreak(..) => true,
1177
1178             _ => contains_exterior_struct_lit(expr),
1179         };
1180
1181         if needs_par {
1182             self.popen()?;
1183         }
1184         self.print_expr(expr)?;
1185         if needs_par {
1186             self.pclose()?;
1187         }
1188         Ok(())
1189     }
1190
1191     fn print_expr_vec(&mut self, exprs: &[hir::Expr]) -> io::Result<()> {
1192         self.ibox(indent_unit)?;
1193         self.s.word("[")?;
1194         self.commasep_exprs(Inconsistent, exprs)?;
1195         self.s.word("]")?;
1196         self.end()
1197     }
1198
1199     fn print_expr_repeat(&mut self, element: &hir::Expr, count: &hir::AnonConst) -> io::Result<()> {
1200         self.ibox(indent_unit)?;
1201         self.s.word("[")?;
1202         self.print_expr(element)?;
1203         self.word_space(";")?;
1204         self.print_anon_const(count)?;
1205         self.s.word("]")?;
1206         self.end()
1207     }
1208
1209     fn print_expr_struct(&mut self,
1210                          qpath: &hir::QPath,
1211                          fields: &[hir::Field],
1212                          wth: &Option<P<hir::Expr>>)
1213                          -> io::Result<()> {
1214         self.print_qpath(qpath, true)?;
1215         self.s.word("{")?;
1216         self.commasep_cmnt(Consistent,
1217                            &fields[..],
1218                            |s, field| {
1219                                s.ibox(indent_unit)?;
1220                                if !field.is_shorthand {
1221                                     s.print_ident(field.ident)?;
1222                                     s.word_space(":")?;
1223                                }
1224                                s.print_expr(&field.expr)?;
1225                                s.end()
1226                            },
1227                            |f| f.span)?;
1228         match *wth {
1229             Some(ref expr) => {
1230                 self.ibox(indent_unit)?;
1231                 if !fields.is_empty() {
1232                     self.s.word(",")?;
1233                     self.s.space()?;
1234                 }
1235                 self.s.word("..")?;
1236                 self.print_expr(&expr)?;
1237                 self.end()?;
1238             }
1239             _ => if !fields.is_empty() {
1240                 self.s.word(",")?
1241             },
1242         }
1243         self.s.word("}")?;
1244         Ok(())
1245     }
1246
1247     fn print_expr_tup(&mut self, exprs: &[hir::Expr]) -> io::Result<()> {
1248         self.popen()?;
1249         self.commasep_exprs(Inconsistent, exprs)?;
1250         if exprs.len() == 1 {
1251             self.s.word(",")?;
1252         }
1253         self.pclose()
1254     }
1255
1256     fn print_expr_call(&mut self, func: &hir::Expr, args: &[hir::Expr]) -> io::Result<()> {
1257         let prec =
1258             match func.node {
1259                 hir::ExprField(..) => parser::PREC_FORCE_PAREN,
1260                 _ => parser::PREC_POSTFIX,
1261             };
1262
1263         self.print_expr_maybe_paren(func, prec)?;
1264         self.print_call_post(args)
1265     }
1266
1267     fn print_expr_method_call(&mut self,
1268                               segment: &hir::PathSegment,
1269                               args: &[hir::Expr])
1270                               -> io::Result<()> {
1271         let base_args = &args[1..];
1272         self.print_expr_maybe_paren(&args[0], parser::PREC_POSTFIX)?;
1273         self.s.word(".")?;
1274         self.print_ident(segment.ident)?;
1275
1276         segment.with_generic_args(|generic_args| {
1277             if !generic_args.args.is_empty() || !generic_args.bindings.is_empty() {
1278                 return self.print_generic_args(&generic_args, segment.infer_types, true);
1279             }
1280             Ok(())
1281         })?;
1282         self.print_call_post(base_args)
1283     }
1284
1285     fn print_expr_binary(&mut self,
1286                          op: hir::BinOp,
1287                          lhs: &hir::Expr,
1288                          rhs: &hir::Expr)
1289                          -> io::Result<()> {
1290         let assoc_op = bin_op_to_assoc_op(op.node);
1291         let prec = assoc_op.precedence() as i8;
1292         let fixity = assoc_op.fixity();
1293
1294         let (left_prec, right_prec) = match fixity {
1295             Fixity::Left => (prec, prec + 1),
1296             Fixity::Right => (prec + 1, prec),
1297             Fixity::None => (prec + 1, prec + 1),
1298         };
1299
1300         let left_prec = match (&lhs.node, op.node) {
1301             // These cases need parens: `x as i32 < y` has the parser thinking that `i32 < y` is
1302             // the beginning of a path type. It starts trying to parse `x as (i32 < y ...` instead
1303             // of `(x as i32) < ...`. We need to convince it _not_ to do that.
1304             (&hir::ExprCast { .. }, hir::BinOp_::BiLt) |
1305             (&hir::ExprCast { .. }, hir::BinOp_::BiShl) => parser::PREC_FORCE_PAREN,
1306             _ => left_prec,
1307         };
1308
1309         self.print_expr_maybe_paren(lhs, left_prec)?;
1310         self.s.space()?;
1311         self.word_space(op.node.as_str())?;
1312         self.print_expr_maybe_paren(rhs, right_prec)
1313     }
1314
1315     fn print_expr_unary(&mut self, op: hir::UnOp, expr: &hir::Expr) -> io::Result<()> {
1316         self.s.word(op.as_str())?;
1317         self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
1318     }
1319
1320     fn print_expr_addr_of(&mut self,
1321                           mutability: hir::Mutability,
1322                           expr: &hir::Expr)
1323                           -> io::Result<()> {
1324         self.s.word("&")?;
1325         self.print_mutability(mutability)?;
1326         self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
1327     }
1328
1329     pub fn print_expr(&mut self, expr: &hir::Expr) -> io::Result<()> {
1330         self.maybe_print_comment(expr.span.lo())?;
1331         self.print_outer_attributes(&expr.attrs)?;
1332         self.ibox(indent_unit)?;
1333         self.ann.pre(self, NodeExpr(expr))?;
1334         match expr.node {
1335             hir::ExprBox(ref expr) => {
1336                 self.word_space("box")?;
1337                 self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)?;
1338             }
1339             hir::ExprArray(ref exprs) => {
1340                 self.print_expr_vec(exprs)?;
1341             }
1342             hir::ExprRepeat(ref element, ref count) => {
1343                 self.print_expr_repeat(&element, count)?;
1344             }
1345             hir::ExprStruct(ref qpath, ref fields, ref wth) => {
1346                 self.print_expr_struct(qpath, &fields[..], wth)?;
1347             }
1348             hir::ExprTup(ref exprs) => {
1349                 self.print_expr_tup(exprs)?;
1350             }
1351             hir::ExprCall(ref func, ref args) => {
1352                 self.print_expr_call(&func, args)?;
1353             }
1354             hir::ExprMethodCall(ref segment, _, ref args) => {
1355                 self.print_expr_method_call(segment, args)?;
1356             }
1357             hir::ExprBinary(op, ref lhs, ref rhs) => {
1358                 self.print_expr_binary(op, &lhs, &rhs)?;
1359             }
1360             hir::ExprUnary(op, ref expr) => {
1361                 self.print_expr_unary(op, &expr)?;
1362             }
1363             hir::ExprAddrOf(m, ref expr) => {
1364                 self.print_expr_addr_of(m, &expr)?;
1365             }
1366             hir::ExprLit(ref lit) => {
1367                 self.print_literal(&lit)?;
1368             }
1369             hir::ExprCast(ref expr, ref ty) => {
1370                 let prec = AssocOp::As.precedence() as i8;
1371                 self.print_expr_maybe_paren(&expr, prec)?;
1372                 self.s.space()?;
1373                 self.word_space("as")?;
1374                 self.print_type(&ty)?;
1375             }
1376             hir::ExprType(ref expr, ref ty) => {
1377                 let prec = AssocOp::Colon.precedence() as i8;
1378                 self.print_expr_maybe_paren(&expr, prec)?;
1379                 self.word_space(":")?;
1380                 self.print_type(&ty)?;
1381             }
1382             hir::ExprIf(ref test, ref blk, ref elseopt) => {
1383                 self.print_if(&test, &blk, elseopt.as_ref().map(|e| &**e))?;
1384             }
1385             hir::ExprWhile(ref test, ref blk, opt_label) => {
1386                 if let Some(label) = opt_label {
1387                     self.print_ident(label.ident)?;
1388                     self.word_space(":")?;
1389                 }
1390                 self.head("while")?;
1391                 self.print_expr_as_cond(&test)?;
1392                 self.s.space()?;
1393                 self.print_block(&blk)?;
1394             }
1395             hir::ExprLoop(ref blk, opt_label, _) => {
1396                 if let Some(label) = opt_label {
1397                     self.print_ident(label.ident)?;
1398                     self.word_space(":")?;
1399                 }
1400                 self.head("loop")?;
1401                 self.s.space()?;
1402                 self.print_block(&blk)?;
1403             }
1404             hir::ExprMatch(ref expr, ref arms, _) => {
1405                 self.cbox(indent_unit)?;
1406                 self.ibox(4)?;
1407                 self.word_nbsp("match")?;
1408                 self.print_expr_as_cond(&expr)?;
1409                 self.s.space()?;
1410                 self.bopen()?;
1411                 for arm in arms {
1412                     self.print_arm(arm)?;
1413                 }
1414                 self.bclose_(expr.span, indent_unit)?;
1415             }
1416             hir::ExprClosure(capture_clause, ref decl, body, _fn_decl_span, _gen) => {
1417                 self.print_capture_clause(capture_clause)?;
1418
1419                 self.print_closure_args(&decl, body)?;
1420                 self.s.space()?;
1421
1422                 // this is a bare expression
1423                 self.ann.nested(self, Nested::Body(body))?;
1424                 self.end()?; // need to close a box
1425
1426                 // a box will be closed by print_expr, but we didn't want an overall
1427                 // wrapper so we closed the corresponding opening. so create an
1428                 // empty box to satisfy the close.
1429                 self.ibox(0)?;
1430             }
1431             hir::ExprBlock(ref blk, opt_label) => {
1432                 if let Some(label) = opt_label {
1433                     self.print_ident(label.ident)?;
1434                     self.word_space(":")?;
1435                 }
1436                 // containing cbox, will be closed by print-block at }
1437                 self.cbox(indent_unit)?;
1438                 // head-box, will be closed by print-block after {
1439                 self.ibox(0)?;
1440                 self.print_block(&blk)?;
1441             }
1442             hir::ExprAssign(ref lhs, ref rhs) => {
1443                 let prec = AssocOp::Assign.precedence() as i8;
1444                 self.print_expr_maybe_paren(&lhs, prec + 1)?;
1445                 self.s.space()?;
1446                 self.word_space("=")?;
1447                 self.print_expr_maybe_paren(&rhs, prec)?;
1448             }
1449             hir::ExprAssignOp(op, ref lhs, ref rhs) => {
1450                 let prec = AssocOp::Assign.precedence() as i8;
1451                 self.print_expr_maybe_paren(&lhs, prec + 1)?;
1452                 self.s.space()?;
1453                 self.s.word(op.node.as_str())?;
1454                 self.word_space("=")?;
1455                 self.print_expr_maybe_paren(&rhs, prec)?;
1456             }
1457             hir::ExprField(ref expr, ident) => {
1458                 self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX)?;
1459                 self.s.word(".")?;
1460                 self.print_ident(ident)?;
1461             }
1462             hir::ExprIndex(ref expr, ref index) => {
1463                 self.print_expr_maybe_paren(&expr, parser::PREC_POSTFIX)?;
1464                 self.s.word("[")?;
1465                 self.print_expr(&index)?;
1466                 self.s.word("]")?;
1467             }
1468             hir::ExprPath(ref qpath) => {
1469                 self.print_qpath(qpath, true)?
1470             }
1471             hir::ExprBreak(destination, ref opt_expr) => {
1472                 self.s.word("break")?;
1473                 self.s.space()?;
1474                 if let Some(label) = destination.label {
1475                     self.print_ident(label.ident)?;
1476                     self.s.space()?;
1477                 }
1478                 if let Some(ref expr) = *opt_expr {
1479                     self.print_expr_maybe_paren(expr, parser::PREC_JUMP)?;
1480                     self.s.space()?;
1481                 }
1482             }
1483             hir::ExprContinue(destination) => {
1484                 self.s.word("continue")?;
1485                 self.s.space()?;
1486                 if let Some(label) = destination.label {
1487                     self.print_ident(label.ident)?;
1488                     self.s.space()?
1489                 }
1490             }
1491             hir::ExprRet(ref result) => {
1492                 self.s.word("return")?;
1493                 match *result {
1494                     Some(ref expr) => {
1495                         self.s.word(" ")?;
1496                         self.print_expr_maybe_paren(&expr, parser::PREC_JUMP)?;
1497                     }
1498                     _ => (),
1499                 }
1500             }
1501             hir::ExprInlineAsm(ref a, ref outputs, ref inputs) => {
1502                 self.s.word("asm!")?;
1503                 self.popen()?;
1504                 self.print_string(&a.asm.as_str(), a.asm_str_style)?;
1505                 self.word_space(":")?;
1506
1507                 let mut out_idx = 0;
1508                 self.commasep(Inconsistent, &a.outputs, |s, out| {
1509                     let constraint = out.constraint.as_str();
1510                     let mut ch = constraint.chars();
1511                     match ch.next() {
1512                         Some('=') if out.is_rw => {
1513                             s.print_string(&format!("+{}", ch.as_str()),
1514                                            ast::StrStyle::Cooked)?
1515                         }
1516                         _ => s.print_string(&constraint, ast::StrStyle::Cooked)?,
1517                     }
1518                     s.popen()?;
1519                     s.print_expr(&outputs[out_idx])?;
1520                     s.pclose()?;
1521                     out_idx += 1;
1522                     Ok(())
1523                 })?;
1524                 self.s.space()?;
1525                 self.word_space(":")?;
1526
1527                 let mut in_idx = 0;
1528                 self.commasep(Inconsistent, &a.inputs, |s, co| {
1529                     s.print_string(&co.as_str(), ast::StrStyle::Cooked)?;
1530                     s.popen()?;
1531                     s.print_expr(&inputs[in_idx])?;
1532                     s.pclose()?;
1533                     in_idx += 1;
1534                     Ok(())
1535                 })?;
1536                 self.s.space()?;
1537                 self.word_space(":")?;
1538
1539                 self.commasep(Inconsistent, &a.clobbers, |s, co| {
1540                     s.print_string(&co.as_str(), ast::StrStyle::Cooked)?;
1541                     Ok(())
1542                 })?;
1543
1544                 let mut options = vec![];
1545                 if a.volatile {
1546                     options.push("volatile");
1547                 }
1548                 if a.alignstack {
1549                     options.push("alignstack");
1550                 }
1551                 if a.dialect == ast::AsmDialect::Intel {
1552                     options.push("intel");
1553                 }
1554
1555                 if !options.is_empty() {
1556                     self.s.space()?;
1557                     self.word_space(":")?;
1558                     self.commasep(Inconsistent, &options, |s, &co| {
1559                         s.print_string(co, ast::StrStyle::Cooked)?;
1560                         Ok(())
1561                     })?;
1562                 }
1563
1564                 self.pclose()?;
1565             }
1566             hir::ExprYield(ref expr) => {
1567                 self.word_space("yield")?;
1568                 self.print_expr_maybe_paren(&expr, parser::PREC_JUMP)?;
1569             }
1570         }
1571         self.ann.post(self, NodeExpr(expr))?;
1572         self.end()
1573     }
1574
1575     pub fn print_local_decl(&mut self, loc: &hir::Local) -> io::Result<()> {
1576         self.print_pat(&loc.pat)?;
1577         if let Some(ref ty) = loc.ty {
1578             self.word_space(":")?;
1579             self.print_type(&ty)?;
1580         }
1581         Ok(())
1582     }
1583
1584     pub fn print_decl(&mut self, decl: &hir::Decl) -> io::Result<()> {
1585         self.maybe_print_comment(decl.span.lo())?;
1586         match decl.node {
1587             hir::DeclLocal(ref loc) => {
1588                 self.space_if_not_bol()?;
1589                 self.ibox(indent_unit)?;
1590                 self.word_nbsp("let")?;
1591
1592                 self.ibox(indent_unit)?;
1593                 self.print_local_decl(&loc)?;
1594                 self.end()?;
1595                 if let Some(ref init) = loc.init {
1596                     self.nbsp()?;
1597                     self.word_space("=")?;
1598                     self.print_expr(&init)?;
1599                 }
1600                 self.end()
1601             }
1602             hir::DeclItem(item) => {
1603                 self.ann.nested(self, Nested::Item(item))
1604             }
1605         }
1606     }
1607
1608     pub fn print_usize(&mut self, i: usize) -> io::Result<()> {
1609         self.s.word(&i.to_string())
1610     }
1611
1612     pub fn print_ident(&mut self, ident: ast::Ident) -> io::Result<()> {
1613         if ident.is_raw_guess() {
1614             self.s.word(&format!("r#{}", ident.name))?;
1615         } else {
1616             self.s.word(&ident.as_str())?;
1617         }
1618         self.ann.post(self, NodeName(&ident.name))
1619     }
1620
1621     pub fn print_name(&mut self, name: ast::Name) -> io::Result<()> {
1622         self.print_ident(ast::Ident::with_empty_ctxt(name))
1623     }
1624
1625     pub fn print_for_decl(&mut self, loc: &hir::Local, coll: &hir::Expr) -> io::Result<()> {
1626         self.print_local_decl(loc)?;
1627         self.s.space()?;
1628         self.word_space("in")?;
1629         self.print_expr(coll)
1630     }
1631
1632     pub fn print_path(&mut self,
1633                       path: &hir::Path,
1634                       colons_before_params: bool)
1635                       -> io::Result<()> {
1636         self.maybe_print_comment(path.span.lo())?;
1637
1638         for (i, segment) in path.segments.iter().enumerate() {
1639             if i > 0 {
1640                 self.s.word("::")?
1641             }
1642             if segment.ident.name != keywords::CrateRoot.name() &&
1643                segment.ident.name != keywords::DollarCrate.name() {
1644                self.print_ident(segment.ident)?;
1645                segment.with_generic_args(|generic_args| {
1646                    self.print_generic_args(generic_args, segment.infer_types,
1647                                            colons_before_params)
1648                })?;
1649             }
1650         }
1651
1652         Ok(())
1653     }
1654
1655     pub fn print_qpath(&mut self,
1656                        qpath: &hir::QPath,
1657                        colons_before_params: bool)
1658                        -> io::Result<()> {
1659         match *qpath {
1660             hir::QPath::Resolved(None, ref path) => {
1661                 self.print_path(path, colons_before_params)
1662             }
1663             hir::QPath::Resolved(Some(ref qself), ref path) => {
1664                 self.s.word("<")?;
1665                 self.print_type(qself)?;
1666                 self.s.space()?;
1667                 self.word_space("as")?;
1668
1669                 for (i, segment) in path.segments[..path.segments.len() - 1].iter().enumerate() {
1670                     if i > 0 {
1671                         self.s.word("::")?
1672                     }
1673                     if segment.ident.name != keywords::CrateRoot.name() &&
1674                        segment.ident.name != keywords::DollarCrate.name() {
1675                         self.print_ident(segment.ident)?;
1676                         segment.with_generic_args(|generic_args| {
1677                             self.print_generic_args(generic_args,
1678                                                     segment.infer_types,
1679                                                     colons_before_params)
1680                         })?;
1681                     }
1682                 }
1683
1684                 self.s.word(">")?;
1685                 self.s.word("::")?;
1686                 let item_segment = path.segments.last().unwrap();
1687                 self.print_ident(item_segment.ident)?;
1688                 item_segment.with_generic_args(|generic_args| {
1689                     self.print_generic_args(generic_args,
1690                                             item_segment.infer_types,
1691                                             colons_before_params)
1692                 })
1693             }
1694             hir::QPath::TypeRelative(ref qself, ref item_segment) => {
1695                 self.s.word("<")?;
1696                 self.print_type(qself)?;
1697                 self.s.word(">")?;
1698                 self.s.word("::")?;
1699                 self.print_ident(item_segment.ident)?;
1700                 item_segment.with_generic_args(|generic_args| {
1701                     self.print_generic_args(generic_args,
1702                                             item_segment.infer_types,
1703                                             colons_before_params)
1704                 })
1705             }
1706         }
1707     }
1708
1709     fn print_generic_args(&mut self,
1710                              generic_args: &hir::GenericArgs,
1711                              infer_types: bool,
1712                              colons_before_params: bool)
1713                              -> io::Result<()> {
1714         if generic_args.parenthesized {
1715             self.s.word("(")?;
1716             self.commasep(Inconsistent, generic_args.inputs(), |s, ty| s.print_type(&ty))?;
1717             self.s.word(")")?;
1718
1719             self.space_if_not_bol()?;
1720             self.word_space("->")?;
1721             self.print_type(&generic_args.bindings[0].ty)?;
1722         } else {
1723             let start = if colons_before_params { "::<" } else { "<" };
1724             let empty = Cell::new(true);
1725             let start_or_comma = |this: &mut Self| {
1726                 if empty.get() {
1727                     empty.set(false);
1728                     this.s.word(start)
1729                 } else {
1730                     this.word_space(",")
1731                 }
1732             };
1733
1734             let mut types = vec![];
1735             let mut elide_lifetimes = true;
1736             for arg in &generic_args.args {
1737                 match arg {
1738                     GenericArg::Lifetime(lt) => {
1739                         if !lt.is_elided() {
1740                             elide_lifetimes = false;
1741                         }
1742                     }
1743                     GenericArg::Type(ty) => {
1744                         types.push(ty);
1745                     }
1746                 }
1747             }
1748             if !elide_lifetimes {
1749                 start_or_comma(self)?;
1750                 self.commasep(Inconsistent, &generic_args.args, |s, generic_arg| {
1751                     match generic_arg {
1752                         GenericArg::Lifetime(lt) => s.print_lifetime(lt),
1753                         GenericArg::Type(ty) => s.print_type(ty),
1754                     }
1755                 })?;
1756             } else if !types.is_empty() {
1757                 start_or_comma(self)?;
1758                 self.commasep(Inconsistent, &types, |s, ty| s.print_type(&ty))?;
1759             }
1760
1761             // FIXME(eddyb) This would leak into error messages, e.g.:
1762             // "non-exhaustive patterns: `Some::<..>(_)` not covered".
1763             if infer_types && false {
1764                 start_or_comma(self)?;
1765                 self.s.word("..")?;
1766             }
1767
1768             for binding in generic_args.bindings.iter() {
1769                 start_or_comma(self)?;
1770                 self.print_ident(binding.ident)?;
1771                 self.s.space()?;
1772                 self.word_space("=")?;
1773                 self.print_type(&binding.ty)?;
1774             }
1775
1776             if !empty.get() {
1777                 self.s.word(">")?
1778             }
1779         }
1780
1781         Ok(())
1782     }
1783
1784     pub fn print_pat(&mut self, pat: &hir::Pat) -> io::Result<()> {
1785         self.maybe_print_comment(pat.span.lo())?;
1786         self.ann.pre(self, NodePat(pat))?;
1787         // Pat isn't normalized, but the beauty of it
1788         // is that it doesn't matter
1789         match pat.node {
1790             PatKind::Wild => self.s.word("_")?,
1791             PatKind::Binding(binding_mode, _, ident, ref sub) => {
1792                 match binding_mode {
1793                     hir::BindingAnnotation::Ref => {
1794                         self.word_nbsp("ref")?;
1795                         self.print_mutability(hir::MutImmutable)?;
1796                     }
1797                     hir::BindingAnnotation::RefMut => {
1798                         self.word_nbsp("ref")?;
1799                         self.print_mutability(hir::MutMutable)?;
1800                     }
1801                     hir::BindingAnnotation::Unannotated => {}
1802                     hir::BindingAnnotation::Mutable => {
1803                         self.word_nbsp("mut")?;
1804                     }
1805                 }
1806                 self.print_ident(ident)?;
1807                 if let Some(ref p) = *sub {
1808                     self.s.word("@")?;
1809                     self.print_pat(&p)?;
1810                 }
1811             }
1812             PatKind::TupleStruct(ref qpath, ref elts, ddpos) => {
1813                 self.print_qpath(qpath, true)?;
1814                 self.popen()?;
1815                 if let Some(ddpos) = ddpos {
1816                     self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(&p))?;
1817                     if ddpos != 0 {
1818                         self.word_space(",")?;
1819                     }
1820                     self.s.word("..")?;
1821                     if ddpos != elts.len() {
1822                         self.s.word(",")?;
1823                         self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(&p))?;
1824                     }
1825                 } else {
1826                     self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(&p))?;
1827                 }
1828                 self.pclose()?;
1829             }
1830             PatKind::Path(ref qpath) => {
1831                 self.print_qpath(qpath, true)?;
1832             }
1833             PatKind::Struct(ref qpath, ref fields, etc) => {
1834                 self.print_qpath(qpath, true)?;
1835                 self.nbsp()?;
1836                 self.word_space("{")?;
1837                 self.commasep_cmnt(Consistent,
1838                                    &fields[..],
1839                                    |s, f| {
1840                                        s.cbox(indent_unit)?;
1841                                        if !f.node.is_shorthand {
1842                                            s.print_ident(f.node.ident)?;
1843                                            s.word_nbsp(":")?;
1844                                        }
1845                                        s.print_pat(&f.node.pat)?;
1846                                        s.end()
1847                                    },
1848                                    |f| f.node.pat.span)?;
1849                 if etc {
1850                     if !fields.is_empty() {
1851                         self.word_space(",")?;
1852                     }
1853                     self.s.word("..")?;
1854                 }
1855                 self.s.space()?;
1856                 self.s.word("}")?;
1857             }
1858             PatKind::Tuple(ref elts, ddpos) => {
1859                 self.popen()?;
1860                 if let Some(ddpos) = ddpos {
1861                     self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(&p))?;
1862                     if ddpos != 0 {
1863                         self.word_space(",")?;
1864                     }
1865                     self.s.word("..")?;
1866                     if ddpos != elts.len() {
1867                         self.s.word(",")?;
1868                         self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(&p))?;
1869                     }
1870                 } else {
1871                     self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(&p))?;
1872                     if elts.len() == 1 {
1873                         self.s.word(",")?;
1874                     }
1875                 }
1876                 self.pclose()?;
1877             }
1878             PatKind::Box(ref inner) => {
1879                 let is_range_inner = match inner.node {
1880                     PatKind::Range(..) => true,
1881                     _ => false,
1882                 };
1883                 self.s.word("box ")?;
1884                 if is_range_inner {
1885                     self.popen()?;
1886                 }
1887                 self.print_pat(&inner)?;
1888                 if is_range_inner {
1889                     self.pclose()?;
1890                 }
1891             }
1892             PatKind::Ref(ref inner, mutbl) => {
1893                 let is_range_inner = match inner.node {
1894                     PatKind::Range(..) => true,
1895                     _ => false,
1896                 };
1897                 self.s.word("&")?;
1898                 if mutbl == hir::MutMutable {
1899                     self.s.word("mut ")?;
1900                 }
1901                 if is_range_inner {
1902                     self.popen()?;
1903                 }
1904                 self.print_pat(&inner)?;
1905                 if is_range_inner {
1906                     self.pclose()?;
1907                 }
1908             }
1909             PatKind::Lit(ref e) => self.print_expr(&e)?,
1910             PatKind::Range(ref begin, ref end, ref end_kind) => {
1911                 self.print_expr(&begin)?;
1912                 self.s.space()?;
1913                 match *end_kind {
1914                     RangeEnd::Included => self.s.word("...")?,
1915                     RangeEnd::Excluded => self.s.word("..")?,
1916                 }
1917                 self.print_expr(&end)?;
1918             }
1919             PatKind::Slice(ref before, ref slice, ref after) => {
1920                 self.s.word("[")?;
1921                 self.commasep(Inconsistent, &before[..], |s, p| s.print_pat(&p))?;
1922                 if let Some(ref p) = *slice {
1923                     if !before.is_empty() {
1924                         self.word_space(",")?;
1925                     }
1926                     if p.node != PatKind::Wild {
1927                         self.print_pat(&p)?;
1928                     }
1929                     self.s.word("..")?;
1930                     if !after.is_empty() {
1931                         self.word_space(",")?;
1932                     }
1933                 }
1934                 self.commasep(Inconsistent, &after[..], |s, p| s.print_pat(&p))?;
1935                 self.s.word("]")?;
1936             }
1937         }
1938         self.ann.post(self, NodePat(pat))
1939     }
1940
1941     fn print_arm(&mut self, arm: &hir::Arm) -> io::Result<()> {
1942         // I have no idea why this check is necessary, but here it
1943         // is :(
1944         if arm.attrs.is_empty() {
1945             self.s.space()?;
1946         }
1947         self.cbox(indent_unit)?;
1948         self.ibox(0)?;
1949         self.print_outer_attributes(&arm.attrs)?;
1950         let mut first = true;
1951         for p in &arm.pats {
1952             if first {
1953                 first = false;
1954             } else {
1955                 self.s.space()?;
1956                 self.word_space("|")?;
1957             }
1958             self.print_pat(&p)?;
1959         }
1960         self.s.space()?;
1961         if let Some(ref e) = arm.guard {
1962             self.word_space("if")?;
1963             self.print_expr(&e)?;
1964             self.s.space()?;
1965         }
1966         self.word_space("=>")?;
1967
1968         match arm.body.node {
1969             hir::ExprBlock(ref blk, opt_label) => {
1970                 if let Some(label) = opt_label {
1971                     self.print_ident(label.ident)?;
1972                     self.word_space(":")?;
1973                 }
1974                 // the block will close the pattern's ibox
1975                 self.print_block_unclosed_indent(&blk, indent_unit)?;
1976
1977                 // If it is a user-provided unsafe block, print a comma after it
1978                 if let hir::UnsafeBlock(hir::UserProvided) = blk.rules {
1979                     self.s.word(",")?;
1980                 }
1981             }
1982             _ => {
1983                 self.end()?; // close the ibox for the pattern
1984                 self.print_expr(&arm.body)?;
1985                 self.s.word(",")?;
1986             }
1987         }
1988         self.end() // close enclosing cbox
1989     }
1990
1991     pub fn print_fn(&mut self,
1992                     decl: &hir::FnDecl,
1993                     header: hir::FnHeader,
1994                     name: Option<ast::Name>,
1995                     generics: &hir::Generics,
1996                     vis: &hir::Visibility,
1997                     arg_names: &[ast::Ident],
1998                     body_id: Option<hir::BodyId>)
1999                     -> io::Result<()> {
2000         self.print_fn_header_info(header, vis)?;
2001
2002         if let Some(name) = name {
2003             self.nbsp()?;
2004             self.print_name(name)?;
2005         }
2006         self.print_generic_params(&generics.params)?;
2007
2008         self.popen()?;
2009         let mut i = 0;
2010         // Make sure we aren't supplied *both* `arg_names` and `body_id`.
2011         assert!(arg_names.is_empty() || body_id.is_none());
2012         self.commasep(Inconsistent, &decl.inputs, |s, ty| {
2013             s.ibox(indent_unit)?;
2014             if let Some(arg_name) = arg_names.get(i) {
2015                 s.s.word(&arg_name.as_str())?;
2016                 s.s.word(":")?;
2017                 s.s.space()?;
2018             } else if let Some(body_id) = body_id {
2019                 s.ann.nested(s, Nested::BodyArgPat(body_id, i))?;
2020                 s.s.word(":")?;
2021                 s.s.space()?;
2022             }
2023             i += 1;
2024             s.print_type(ty)?;
2025             s.end()
2026         })?;
2027         if decl.variadic {
2028             self.s.word(", ...")?;
2029         }
2030         self.pclose()?;
2031
2032         self.print_fn_output(decl)?;
2033         self.print_where_clause(&generics.where_clause)
2034     }
2035
2036     fn print_closure_args(&mut self, decl: &hir::FnDecl, body_id: hir::BodyId) -> io::Result<()> {
2037         self.s.word("|")?;
2038         let mut i = 0;
2039         self.commasep(Inconsistent, &decl.inputs, |s, ty| {
2040             s.ibox(indent_unit)?;
2041
2042             s.ann.nested(s, Nested::BodyArgPat(body_id, i))?;
2043             i += 1;
2044
2045             if ty.node != hir::TyInfer {
2046                 s.s.word(":")?;
2047                 s.s.space()?;
2048                 s.print_type(ty)?;
2049             }
2050             s.end()
2051         })?;
2052         self.s.word("|")?;
2053
2054         if let hir::DefaultReturn(..) = decl.output {
2055             return Ok(());
2056         }
2057
2058         self.space_if_not_bol()?;
2059         self.word_space("->")?;
2060         match decl.output {
2061             hir::Return(ref ty) => {
2062                 self.print_type(&ty)?;
2063                 self.maybe_print_comment(ty.span.lo())
2064             }
2065             hir::DefaultReturn(..) => unreachable!(),
2066         }
2067     }
2068
2069     pub fn print_capture_clause(&mut self, capture_clause: hir::CaptureClause) -> io::Result<()> {
2070         match capture_clause {
2071             hir::CaptureByValue => self.word_space("move"),
2072             hir::CaptureByRef => Ok(()),
2073         }
2074     }
2075
2076     pub fn print_bounds(&mut self, prefix: &str, bounds: &[hir::GenericBound]) -> io::Result<()> {
2077         if !bounds.is_empty() {
2078             self.s.word(prefix)?;
2079             let mut first = true;
2080             for bound in bounds {
2081                 if !(first && prefix.is_empty()) {
2082                     self.nbsp()?;
2083                 }
2084                 if first {
2085                     first = false;
2086                 } else {
2087                     self.word_space("+")?;
2088                 }
2089
2090                 match bound {
2091                     GenericBound::Trait(tref, modifier) => {
2092                         if modifier == &TraitBoundModifier::Maybe {
2093                             self.s.word("?")?;
2094                         }
2095                         self.print_poly_trait_ref(tref)?;
2096                     }
2097                     GenericBound::Outlives(lt) => {
2098                         self.print_lifetime(lt)?;
2099                     }
2100                 }
2101             }
2102         }
2103         Ok(())
2104     }
2105
2106     pub fn print_generic_params(&mut self, generic_params: &[GenericParam]) -> io::Result<()> {
2107         if !generic_params.is_empty() {
2108             self.s.word("<")?;
2109
2110             self.commasep(Inconsistent, generic_params, |s, param| {
2111                 s.print_generic_param(param)
2112             })?;
2113
2114             self.s.word(">")?;
2115         }
2116         Ok(())
2117     }
2118
2119     pub fn print_generic_param(&mut self, param: &GenericParam) -> io::Result<()> {
2120         self.print_ident(param.name.ident())?;
2121         match param.kind {
2122             GenericParamKind::Lifetime { .. } => {
2123                 let mut sep = ":";
2124                 for bound in &param.bounds {
2125                     match bound {
2126                         GenericBound::Outlives(lt) => {
2127                             self.s.word(sep)?;
2128                             self.print_lifetime(lt)?;
2129                             sep = "+";
2130                         }
2131                         _ => bug!(),
2132                     }
2133                 }
2134                 Ok(())
2135             }
2136             GenericParamKind::Type { ref default, .. } => {
2137                 self.print_bounds(":", &param.bounds)?;
2138                 match default {
2139                     Some(default) => {
2140                         self.s.space()?;
2141                         self.word_space("=")?;
2142                         self.print_type(&default)
2143                     }
2144                     _ => Ok(()),
2145                 }
2146             }
2147         }
2148     }
2149
2150     pub fn print_lifetime(&mut self, lifetime: &hir::Lifetime) -> io::Result<()> {
2151         self.print_ident(lifetime.name.ident())
2152     }
2153
2154     pub fn print_where_clause(&mut self, where_clause: &hir::WhereClause) -> io::Result<()> {
2155         if where_clause.predicates.is_empty() {
2156             return Ok(());
2157         }
2158
2159         self.s.space()?;
2160         self.word_space("where")?;
2161
2162         for (i, predicate) in where_clause.predicates.iter().enumerate() {
2163             if i != 0 {
2164                 self.word_space(",")?;
2165             }
2166
2167             match predicate {
2168                 &hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
2169                     ref bound_generic_params,
2170                     ref bounded_ty,
2171                     ref bounds,
2172                     ..
2173                 }) => {
2174                     self.print_formal_generic_params(bound_generic_params)?;
2175                     self.print_type(&bounded_ty)?;
2176                     self.print_bounds(":", bounds)?;
2177                 }
2178                 &hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate{ref lifetime,
2179                                                                                 ref bounds,
2180                                                                                 ..}) => {
2181                     self.print_lifetime(lifetime)?;
2182                     self.s.word(":")?;
2183
2184                     for (i, bound) in bounds.iter().enumerate() {
2185                         match bound {
2186                             GenericBound::Outlives(lt) => {
2187                                 self.print_lifetime(lt)?;
2188                             }
2189                             _ => bug!(),
2190                         }
2191
2192                         if i != 0 {
2193                             self.s.word(":")?;
2194                         }
2195                     }
2196                 }
2197                 &hir::WherePredicate::EqPredicate(hir::WhereEqPredicate{ref lhs_ty,
2198                                                                         ref rhs_ty,
2199                                                                         ..}) => {
2200                     self.print_type(lhs_ty)?;
2201                     self.s.space()?;
2202                     self.word_space("=")?;
2203                     self.print_type(rhs_ty)?;
2204                 }
2205             }
2206         }
2207
2208         Ok(())
2209     }
2210
2211     pub fn print_mutability(&mut self, mutbl: hir::Mutability) -> io::Result<()> {
2212         match mutbl {
2213             hir::MutMutable => self.word_nbsp("mut"),
2214             hir::MutImmutable => Ok(()),
2215         }
2216     }
2217
2218     pub fn print_mt(&mut self, mt: &hir::MutTy) -> io::Result<()> {
2219         self.print_mutability(mt.mutbl)?;
2220         self.print_type(&mt.ty)
2221     }
2222
2223     pub fn print_fn_output(&mut self, decl: &hir::FnDecl) -> io::Result<()> {
2224         if let hir::DefaultReturn(..) = decl.output {
2225             return Ok(());
2226         }
2227
2228         self.space_if_not_bol()?;
2229         self.ibox(indent_unit)?;
2230         self.word_space("->")?;
2231         match decl.output {
2232             hir::DefaultReturn(..) => unreachable!(),
2233             hir::Return(ref ty) => self.print_type(&ty)?,
2234         }
2235         self.end()?;
2236
2237         match decl.output {
2238             hir::Return(ref output) => self.maybe_print_comment(output.span.lo()),
2239             _ => Ok(()),
2240         }
2241     }
2242
2243     pub fn print_ty_fn(&mut self,
2244                        abi: Abi,
2245                        unsafety: hir::Unsafety,
2246                        decl: &hir::FnDecl,
2247                        name: Option<ast::Name>,
2248                        generic_params: &[hir::GenericParam],
2249                        arg_names: &[ast::Ident])
2250                        -> io::Result<()> {
2251         self.ibox(indent_unit)?;
2252         if !generic_params.is_empty() {
2253             self.s.word("for")?;
2254             self.print_generic_params(generic_params)?;
2255         }
2256         let generics = hir::Generics {
2257             params: hir::HirVec::new(),
2258             where_clause: hir::WhereClause {
2259                 id: ast::DUMMY_NODE_ID,
2260                 predicates: hir::HirVec::new(),
2261             },
2262             span: syntax_pos::DUMMY_SP,
2263         };
2264         self.print_fn(decl,
2265                       hir::FnHeader {
2266                           unsafety,
2267                           abi,
2268                           constness: hir::Constness::NotConst,
2269                           asyncness: hir::IsAsync::NotAsync,
2270                       },
2271                       name,
2272                       &generics,
2273                       &Spanned { span: syntax_pos::DUMMY_SP,
2274                                  node: hir::VisibilityKind::Inherited },
2275                       arg_names,
2276                       None)?;
2277         self.end()
2278     }
2279
2280     pub fn maybe_print_trailing_comment(&mut self,
2281                                         span: syntax_pos::Span,
2282                                         next_pos: Option<BytePos>)
2283                                         -> io::Result<()> {
2284         let cm = match self.cm {
2285             Some(cm) => cm,
2286             _ => return Ok(()),
2287         };
2288         if let Some(ref cmnt) = self.next_comment() {
2289             if (*cmnt).style != comments::Trailing {
2290                 return Ok(());
2291             }
2292             let span_line = cm.lookup_char_pos(span.hi());
2293             let comment_line = cm.lookup_char_pos((*cmnt).pos);
2294             let mut next = (*cmnt).pos + BytePos(1);
2295             if let Some(p) = next_pos {
2296                 next = p;
2297             }
2298             if span.hi() < (*cmnt).pos && (*cmnt).pos < next &&
2299                span_line.line == comment_line.line {
2300                 self.print_comment(cmnt)?;
2301             }
2302         }
2303         Ok(())
2304     }
2305
2306     pub fn print_remaining_comments(&mut self) -> io::Result<()> {
2307         // If there aren't any remaining comments, then we need to manually
2308         // make sure there is a line break at the end.
2309         if self.next_comment().is_none() {
2310             self.s.hardbreak()?;
2311         }
2312         while let Some(ref cmnt) = self.next_comment() {
2313             self.print_comment(cmnt)?
2314         }
2315         Ok(())
2316     }
2317
2318     pub fn print_opt_abi_and_extern_if_nondefault(&mut self,
2319                                                   opt_abi: Option<Abi>)
2320                                                   -> io::Result<()> {
2321         match opt_abi {
2322             Some(Abi::Rust) => Ok(()),
2323             Some(abi) => {
2324                 self.word_nbsp("extern")?;
2325                 self.word_nbsp(&abi.to_string())
2326             }
2327             None => Ok(()),
2328         }
2329     }
2330
2331     pub fn print_extern_opt_abi(&mut self, opt_abi: Option<Abi>) -> io::Result<()> {
2332         match opt_abi {
2333             Some(abi) => {
2334                 self.word_nbsp("extern")?;
2335                 self.word_nbsp(&abi.to_string())
2336             }
2337             None => Ok(()),
2338         }
2339     }
2340
2341     pub fn print_fn_header_info(&mut self,
2342                                 header: hir::FnHeader,
2343                                 vis: &hir::Visibility)
2344                                 -> io::Result<()> {
2345         self.s.word(&visibility_qualified(vis, ""))?;
2346
2347         match header.constness {
2348             hir::Constness::NotConst => {}
2349             hir::Constness::Const => self.word_nbsp("const")?,
2350         }
2351
2352         match header.asyncness {
2353             hir::IsAsync::NotAsync => {}
2354             hir::IsAsync::Async => self.word_nbsp("async")?,
2355         }
2356
2357         self.print_unsafety(header.unsafety)?;
2358
2359         if header.abi != Abi::Rust {
2360             self.word_nbsp("extern")?;
2361             self.word_nbsp(&header.abi.to_string())?;
2362         }
2363
2364         self.s.word("fn")
2365     }
2366
2367     pub fn print_unsafety(&mut self, s: hir::Unsafety) -> io::Result<()> {
2368         match s {
2369             hir::Unsafety::Normal => Ok(()),
2370             hir::Unsafety::Unsafe => self.word_nbsp("unsafe"),
2371         }
2372     }
2373
2374     pub fn print_is_auto(&mut self, s: hir::IsAuto) -> io::Result<()> {
2375         match s {
2376             hir::IsAuto::Yes => self.word_nbsp("auto"),
2377             hir::IsAuto::No => Ok(()),
2378         }
2379     }
2380 }
2381
2382 // Dup'ed from parse::classify, but adapted for the HIR.
2383 /// Does this expression require a semicolon to be treated
2384 /// as a statement? The negation of this: 'can this expression
2385 /// be used as a statement without a semicolon' -- is used
2386 /// as an early-bail-out in the parser so that, for instance,
2387 ///     if true {...} else {...}
2388 ///      |x| 5
2389 /// isn't parsed as (if true {...} else {...} | x) | 5
2390 fn expr_requires_semi_to_be_stmt(e: &hir::Expr) -> bool {
2391     match e.node {
2392         hir::ExprIf(..) |
2393         hir::ExprMatch(..) |
2394         hir::ExprBlock(..) |
2395         hir::ExprWhile(..) |
2396         hir::ExprLoop(..) => false,
2397         _ => true,
2398     }
2399 }
2400
2401 /// this statement requires a semicolon after it.
2402 /// note that in one case (stmt_semi), we've already
2403 /// seen the semicolon, and thus don't need another.
2404 fn stmt_ends_with_semi(stmt: &hir::Stmt_) -> bool {
2405     match *stmt {
2406         hir::StmtDecl(ref d, _) => {
2407             match d.node {
2408                 hir::DeclLocal(_) => true,
2409                 hir::DeclItem(_) => false,
2410             }
2411         }
2412         hir::StmtExpr(ref e, _) => {
2413             expr_requires_semi_to_be_stmt(&e)
2414         }
2415         hir::StmtSemi(..) => {
2416             false
2417         }
2418     }
2419 }
2420
2421 fn bin_op_to_assoc_op(op: hir::BinOp_) -> AssocOp {
2422     use hir::BinOp_::*;
2423     match op {
2424         BiAdd => AssocOp::Add,
2425         BiSub => AssocOp::Subtract,
2426         BiMul => AssocOp::Multiply,
2427         BiDiv => AssocOp::Divide,
2428         BiRem => AssocOp::Modulus,
2429
2430         BiAnd => AssocOp::LAnd,
2431         BiOr => AssocOp::LOr,
2432
2433         BiBitXor => AssocOp::BitXor,
2434         BiBitAnd => AssocOp::BitAnd,
2435         BiBitOr => AssocOp::BitOr,
2436         BiShl => AssocOp::ShiftLeft,
2437         BiShr => AssocOp::ShiftRight,
2438
2439         BiEq => AssocOp::Equal,
2440         BiLt => AssocOp::Less,
2441         BiLe => AssocOp::LessEqual,
2442         BiNe => AssocOp::NotEqual,
2443         BiGe => AssocOp::GreaterEqual,
2444         BiGt => AssocOp::Greater,
2445     }
2446 }
2447
2448 /// Expressions that syntactically contain an "exterior" struct literal i.e. not surrounded by any
2449 /// parens or other delimiters, e.g. `X { y: 1 }`, `X { y: 1 }.method()`, `foo == X { y: 1 }` and
2450 /// `X { y: 1 } == foo` all do, but `(X { y: 1 }) == foo` does not.
2451 fn contains_exterior_struct_lit(value: &hir::Expr) -> bool {
2452     match value.node {
2453         hir::ExprStruct(..) => true,
2454
2455         hir::ExprAssign(ref lhs, ref rhs) |
2456         hir::ExprAssignOp(_, ref lhs, ref rhs) |
2457         hir::ExprBinary(_, ref lhs, ref rhs) => {
2458             // X { y: 1 } + X { y: 2 }
2459             contains_exterior_struct_lit(&lhs) || contains_exterior_struct_lit(&rhs)
2460         }
2461         hir::ExprUnary(_, ref x) |
2462         hir::ExprCast(ref x, _) |
2463         hir::ExprType(ref x, _) |
2464         hir::ExprField(ref x, _) |
2465         hir::ExprIndex(ref x, _) => {
2466             // &X { y: 1 }, X { y: 1 }.y
2467             contains_exterior_struct_lit(&x)
2468         }
2469
2470         hir::ExprMethodCall(.., ref exprs) => {
2471             // X { y: 1 }.bar(...)
2472             contains_exterior_struct_lit(&exprs[0])
2473         }
2474
2475         _ => false,
2476     }
2477 }