src/librustc/hir/print.rs

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