src/librustc_ast_pretty/pprust.rs

   1 use crate::pp::Breaks::{Consistent, Inconsistent};
   2 use crate::pp::{self, Breaks};
   3
   4 use rustc_span::edition::Edition;
   5 use rustc_span::source_map::{dummy_spanned, SourceMap, Spanned};
   6 use rustc_span::symbol::{kw, sym};
   7 use rustc_span::{BytePos, FileName, Span};
   8 use syntax::ast::{self, BlockCheckMode, PatKind, RangeEnd, RangeSyntax};
   9 use syntax::ast::{Attribute, GenericArg, MacArgs};
  10 use syntax::ast::{GenericBound, SelfKind, TraitBoundModifier};
  11 use syntax::attr;
  12 use syntax::ptr::P;
  13 use syntax::token::{self, BinOpToken, DelimToken, Nonterminal, Token, TokenKind};
  14 use syntax::tokenstream::{self, TokenStream, TokenTree};
  15 use syntax::util::parser::{self, AssocOp, Fixity};
  16 use syntax::util::{classify, comments};
  17
  18 use std::borrow::Cow;
  19
  20 #[cfg(test)]
  21 mod tests;
  22
  23 pub enum MacHeader<'a> {
  24     Path(&'a ast::Path),
  25     Keyword(&'static str),
  26 }
  27
  28 pub enum AnnNode<'a> {
  29     Ident(&'a ast::Ident),
  30     Name(&'a ast::Name),
  31     Block(&'a ast::Block),
  32     Item(&'a ast::Item),
  33     SubItem(ast::NodeId),
  34     Expr(&'a ast::Expr),
  35     Pat(&'a ast::Pat),
  36     Crate(&'a ast::Crate),
  37 }
  38
  39 pub trait PpAnn {
  40     fn pre(&self, _state: &mut State<'_>, _node: AnnNode<'_>) {}
  41     fn post(&self, _state: &mut State<'_>, _node: AnnNode<'_>) {}
  42 }
  43
  44 #[derive(Copy, Clone)]
  45 pub struct NoAnn;
  46
  47 impl PpAnn for NoAnn {}
  48
  49 pub struct Comments<'a> {
  50     cm: &'a SourceMap,
  51     comments: Vec<comments::Comment>,
  52     current: usize,
  53 }
  54
  55 impl<'a> Comments<'a> {
  56     pub fn new(cm: &'a SourceMap, filename: FileName, input: String) -> Comments<'a> {
  57         let comments = comments::gather_comments(cm, filename, input);
  58         Comments { cm, comments, current: 0 }
  59     }
  60
  61     pub fn next(&self) -> Option<comments::Comment> {
  62         self.comments.get(self.current).cloned()
  63     }
  64
  65     pub fn trailing_comment(
  66         &mut self,
  67         span: rustc_span::Span,
  68         next_pos: Option<BytePos>,
  69     ) -> Option<comments::Comment> {
  70         if let Some(cmnt) = self.next() {
  71             if cmnt.style != comments::Trailing {
  72                 return None;
  73             }
  74             let span_line = self.cm.lookup_char_pos(span.hi());
  75             let comment_line = self.cm.lookup_char_pos(cmnt.pos);
  76             let next = next_pos.unwrap_or_else(|| cmnt.pos + BytePos(1));
  77             if span.hi() < cmnt.pos && cmnt.pos < next && span_line.line == comment_line.line {
  78                 return Some(cmnt);
  79             }
  80         }
  81
  82         None
  83     }
  84 }
  85
  86 pub struct State<'a> {
  87     pub s: pp::Printer,
  88     comments: Option<Comments<'a>>,
  89     ann: &'a (dyn PpAnn + 'a),
  90     is_expanded: bool,
  91 }
  92
  93 crate const INDENT_UNIT: usize = 4;
  94
  95 /// Requires you to pass an input filename and reader so that
  96 /// it can scan the input text for comments to copy forward.
  97 pub fn print_crate<'a>(
  98     cm: &'a SourceMap,
  99     krate: &ast::Crate,
 100     filename: FileName,
 101     input: String,
 102     ann: &'a dyn PpAnn,
 103     is_expanded: bool,
 104     edition: Edition,
 105     has_injected_crate: bool,
 106 ) -> String {
 107     let mut s = State {
 108         s: pp::mk_printer(),
 109         comments: Some(Comments::new(cm, filename, input)),
 110         ann,
 111         is_expanded,
 112     };
 113
 114     if is_expanded && has_injected_crate {
 115         // We need to print `#![no_std]` (and its feature gate) so that
 116         // compiling pretty-printed source won't inject libstd again.
 117         // However, we don't want these attributes in the AST because
 118         // of the feature gate, so we fake them up here.
 119
 120         // `#![feature(prelude_import)]`
 121         let pi_nested = attr::mk_nested_word_item(ast::Ident::with_dummy_span(sym::prelude_import));
 122         let list = attr::mk_list_item(ast::Ident::with_dummy_span(sym::feature), vec![pi_nested]);
 123         let fake_attr = attr::mk_attr_inner(list);
 124         s.print_attribute(&fake_attr);
 125
 126         // Currently, in Rust 2018 we don't have `extern crate std;` at the crate
 127         // root, so this is not needed, and actually breaks things.
 128         if edition == Edition::Edition2015 {
 129             // `#![no_std]`
 130             let no_std_meta = attr::mk_word_item(ast::Ident::with_dummy_span(sym::no_std));
 131             let fake_attr = attr::mk_attr_inner(no_std_meta);
 132             s.print_attribute(&fake_attr);
 133         }
 134     }
 135
 136     s.print_mod(&krate.module, &krate.attrs);
 137     s.print_remaining_comments();
 138     s.ann.post(&mut s, AnnNode::Crate(krate));
 139     s.s.eof()
 140 }
 141
 142 pub fn to_string(f: impl FnOnce(&mut State<'_>)) -> String {
 143     let mut printer =
 144         State { s: pp::mk_printer(), comments: None, ann: &NoAnn, is_expanded: false };
 145     f(&mut printer);
 146     printer.s.eof()
 147 }
 148
 149 // This makes comma-separated lists look slightly nicer,
 150 // and also addresses a specific regression described in issue #63896.
 151 fn tt_prepend_space(tt: &TokenTree) -> bool {
 152     match tt {
 153         TokenTree::Token(token) => match token.kind {
 154             token::Comma => false,
 155             _ => true,
 156         },
 157         _ => true,
 158     }
 159 }
 160
 161 fn binop_to_string(op: BinOpToken) -> &'static str {
 162     match op {
 163         token::Plus => "+",
 164         token::Minus => "-",
 165         token::Star => "*",
 166         token::Slash => "/",
 167         token::Percent => "%",
 168         token::Caret => "^",
 169         token::And => "&",
 170         token::Or => "|",
 171         token::Shl => "<<",
 172         token::Shr => ">>",
 173     }
 174 }
 175
 176 pub fn literal_to_string(lit: token::Lit) -> String {
 177     let token::Lit { kind, symbol, suffix } = lit;
 178     let mut out = match kind {
 179         token::Byte => format!("b'{}'", symbol),
 180         token::Char => format!("'{}'", symbol),
 181         token::Str => format!("\"{}\"", symbol),
 182         token::StrRaw(n) => {
 183             format!("r{delim}\"{string}\"{delim}", delim = "#".repeat(n as usize), string = symbol)
 184         }
 185         token::ByteStr => format!("b\"{}\"", symbol),
 186         token::ByteStrRaw(n) => {
 187             format!("br{delim}\"{string}\"{delim}", delim = "#".repeat(n as usize), string = symbol)
 188         }
 189         token::Integer | token::Float | token::Bool | token::Err => symbol.to_string(),
 190     };
 191
 192     if let Some(suffix) = suffix {
 193         out.push_str(&suffix.as_str())
 194     }
 195
 196     out
 197 }
 198
 199 /// Print an ident from AST, `$crate` is converted into its respective crate name.
 200 pub fn ast_ident_to_string(ident: ast::Ident, is_raw: bool) -> String {
 201     ident_to_string(ident.name, is_raw, Some(ident.span))
 202 }
 203
 204 // AST pretty-printer is used as a fallback for turning AST structures into token streams for
 205 // proc macros. Additionally, proc macros may stringify their input and expect it survive the
 206 // stringification (especially true for proc macro derives written between Rust 1.15 and 1.30).
 207 // So we need to somehow pretty-print `$crate` in a way preserving at least some of its
 208 // hygiene data, most importantly name of the crate it refers to.
 209 // As a result we print `$crate` as `crate` if it refers to the local crate
 210 // and as `::other_crate_name` if it refers to some other crate.
 211 // Note, that this is only done if the ident token is printed from inside of AST pretty-pringing,
 212 // but not otherwise. Pretty-printing is the only way for proc macros to discover token contents,
 213 // so we should not perform this lossy conversion if the top level call to the pretty-printer was
 214 // done for a token stream or a single token.
 215 fn ident_to_string(name: ast::Name, is_raw: bool, convert_dollar_crate: Option<Span>) -> String {
 216     if is_raw {
 217         format!("r#{}", name)
 218     } else {
 219         if name == kw::DollarCrate {
 220             if let Some(span) = convert_dollar_crate {
 221                 let converted = span.ctxt().dollar_crate_name();
 222                 return if converted.is_path_segment_keyword() {
 223                     converted.to_string()
 224                 } else {
 225                     format!("::{}", converted)
 226                 };
 227             }
 228         }
 229         name.to_string()
 230     }
 231 }
 232
 233 /// Print the token kind precisely, without converting `$crate` into its respective crate name.
 234 pub fn token_kind_to_string(tok: &TokenKind) -> String {
 235     token_kind_to_string_ext(tok, None)
 236 }
 237
 238 fn token_kind_to_string_ext(tok: &TokenKind, convert_dollar_crate: Option<Span>) -> String {
 239     match *tok {
 240         token::Eq => "=".to_string(),
 241         token::Lt => "<".to_string(),
 242         token::Le => "<=".to_string(),
 243         token::EqEq => "==".to_string(),
 244         token::Ne => "!=".to_string(),
 245         token::Ge => ">=".to_string(),
 246         token::Gt => ">".to_string(),
 247         token::Not => "!".to_string(),
 248         token::Tilde => "~".to_string(),
 249         token::OrOr => "||".to_string(),
 250         token::AndAnd => "&&".to_string(),
 251         token::BinOp(op) => binop_to_string(op).to_string(),
 252         token::BinOpEq(op) => format!("{}=", binop_to_string(op)),
 253
 254         /* Structural symbols */
 255         token::At => "@".to_string(),
 256         token::Dot => ".".to_string(),
 257         token::DotDot => "..".to_string(),
 258         token::DotDotDot => "...".to_string(),
 259         token::DotDotEq => "..=".to_string(),
 260         token::Comma => ",".to_string(),
 261         token::Semi => ";".to_string(),
 262         token::Colon => ":".to_string(),
 263         token::ModSep => "::".to_string(),
 264         token::RArrow => "->".to_string(),
 265         token::LArrow => "<-".to_string(),
 266         token::FatArrow => "=>".to_string(),
 267         token::OpenDelim(token::Paren) => "(".to_string(),
 268         token::CloseDelim(token::Paren) => ")".to_string(),
 269         token::OpenDelim(token::Bracket) => "[".to_string(),
 270         token::CloseDelim(token::Bracket) => "]".to_string(),
 271         token::OpenDelim(token::Brace) => "{".to_string(),
 272         token::CloseDelim(token::Brace) => "}".to_string(),
 273         token::OpenDelim(token::NoDelim) | token::CloseDelim(token::NoDelim) => " ".to_string(),
 274         token::Pound => "#".to_string(),
 275         token::Dollar => "$".to_string(),
 276         token::Question => "?".to_string(),
 277         token::SingleQuote => "'".to_string(),
 278
 279         /* Literals */
 280         token::Literal(lit) => literal_to_string(lit),
 281
 282         /* Name components */
 283         token::Ident(s, is_raw) => ident_to_string(s, is_raw, convert_dollar_crate),
 284         token::Lifetime(s) => s.to_string(),
 285
 286         /* Other */
 287         token::DocComment(s) => s.to_string(),
 288         token::Eof => "<eof>".to_string(),
 289         token::Whitespace => " ".to_string(),
 290         token::Comment => "/* */".to_string(),
 291         token::Shebang(s) => format!("/* shebang: {}*/", s),
 292         token::Unknown(s) => s.to_string(),
 293
 294         token::Interpolated(ref nt) => nonterminal_to_string(nt),
 295     }
 296 }
 297
 298 /// Print the token precisely, without converting `$crate` into its respective crate name.
 299 pub fn token_to_string(token: &Token) -> String {
 300     token_to_string_ext(token, false)
 301 }
 302
 303 fn token_to_string_ext(token: &Token, convert_dollar_crate: bool) -> String {
 304     let convert_dollar_crate = convert_dollar_crate.then_some(token.span);
 305     token_kind_to_string_ext(&token.kind, convert_dollar_crate)
 306 }
 307
 308 pub fn nonterminal_to_string(nt: &Nonterminal) -> String {
 309     match *nt {
 310         token::NtExpr(ref e) => expr_to_string(e),
 311         token::NtMeta(ref e) => attr_item_to_string(e),
 312         token::NtTy(ref e) => ty_to_string(e),
 313         token::NtPath(ref e) => path_to_string(e),
 314         token::NtItem(ref e) => item_to_string(e),
 315         token::NtBlock(ref e) => block_to_string(e),
 316         token::NtStmt(ref e) => stmt_to_string(e),
 317         token::NtPat(ref e) => pat_to_string(e),
 318         token::NtIdent(e, is_raw) => ast_ident_to_string(e, is_raw),
 319         token::NtLifetime(e) => e.to_string(),
 320         token::NtLiteral(ref e) => expr_to_string(e),
 321         token::NtTT(ref tree) => tt_to_string(tree.clone()),
 322         // FIXME(Centril): merge these variants.
 323         token::NtImplItem(ref e) | token::NtTraitItem(ref e) => assoc_item_to_string(e),
 324         token::NtVis(ref e) => vis_to_string(e),
 325         token::NtForeignItem(ref e) => foreign_item_to_string(e),
 326     }
 327 }
 328
 329 pub fn ty_to_string(ty: &ast::Ty) -> String {
 330     to_string(|s| s.print_type(ty))
 331 }
 332
 333 pub fn bounds_to_string(bounds: &[ast::GenericBound]) -> String {
 334     to_string(|s| s.print_type_bounds("", bounds))
 335 }
 336
 337 pub fn pat_to_string(pat: &ast::Pat) -> String {
 338     to_string(|s| s.print_pat(pat))
 339 }
 340
 341 pub fn expr_to_string(e: &ast::Expr) -> String {
 342     to_string(|s| s.print_expr(e))
 343 }
 344
 345 pub fn tt_to_string(tt: tokenstream::TokenTree) -> String {
 346     to_string(|s| s.print_tt(tt, false))
 347 }
 348
 349 pub fn tts_to_string(tokens: TokenStream) -> String {
 350     to_string(|s| s.print_tts(tokens, false))
 351 }
 352
 353 pub fn stmt_to_string(stmt: &ast::Stmt) -> String {
 354     to_string(|s| s.print_stmt(stmt))
 355 }
 356
 357 pub fn item_to_string(i: &ast::Item) -> String {
 358     to_string(|s| s.print_item(i))
 359 }
 360
 361 fn assoc_item_to_string(i: &ast::AssocItem) -> String {
 362     to_string(|s| s.print_assoc_item(i))
 363 }
 364
 365 pub fn generic_params_to_string(generic_params: &[ast::GenericParam]) -> String {
 366     to_string(|s| s.print_generic_params(generic_params))
 367 }
 368
 369 pub fn path_to_string(p: &ast::Path) -> String {
 370     to_string(|s| s.print_path(p, false, 0))
 371 }
 372
 373 pub fn path_segment_to_string(p: &ast::PathSegment) -> String {
 374     to_string(|s| s.print_path_segment(p, false))
 375 }
 376
 377 pub fn vis_to_string(v: &ast::Visibility) -> String {
 378     to_string(|s| s.print_visibility(v))
 379 }
 380
 381 fn block_to_string(blk: &ast::Block) -> String {
 382     to_string(|s| {
 383         // Containing cbox, will be closed by `print_block` at `}`.
 384         s.cbox(INDENT_UNIT);
 385         // Head-ibox, will be closed by `print_block` after `{`.
 386         s.ibox(0);
 387         s.print_block(blk)
 388     })
 389 }
 390
 391 pub fn meta_list_item_to_string(li: &ast::NestedMetaItem) -> String {
 392     to_string(|s| s.print_meta_list_item(li))
 393 }
 394
 395 fn attr_item_to_string(ai: &ast::AttrItem) -> String {
 396     to_string(|s| s.print_attr_item(ai, ai.path.span))
 397 }
 398
 399 pub fn attribute_to_string(attr: &ast::Attribute) -> String {
 400     to_string(|s| s.print_attribute(attr))
 401 }
 402
 403 pub fn param_to_string(arg: &ast::Param) -> String {
 404     to_string(|s| s.print_param(arg, false))
 405 }
 406
 407 fn foreign_item_to_string(arg: &ast::ForeignItem) -> String {
 408     to_string(|s| s.print_foreign_item(arg))
 409 }
 410
 411 fn visibility_qualified(vis: &ast::Visibility, s: &str) -> String {
 412     format!("{}{}", to_string(|s| s.print_visibility(vis)), s)
 413 }
 414
 415 impl std::ops::Deref for State<'_> {
 416     type Target = pp::Printer;
 417     fn deref(&self) -> &Self::Target {
 418         &self.s
 419     }
 420 }
 421
 422 impl std::ops::DerefMut for State<'_> {
 423     fn deref_mut(&mut self) -> &mut Self::Target {
 424         &mut self.s
 425     }
 426 }
 427
 428 pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::DerefMut {
 429     fn comments(&mut self) -> &mut Option<Comments<'a>>;
 430     fn print_ident(&mut self, ident: ast::Ident);
 431     fn print_generic_args(&mut self, args: &ast::GenericArgs, colons_before_params: bool);
 432
 433     fn strsep<T, F>(
 434         &mut self,
 435         sep: &'static str,
 436         space_before: bool,
 437         b: Breaks,
 438         elts: &[T],
 439         mut op: F,
 440     ) where
 441         F: FnMut(&mut Self, &T),
 442     {
 443         self.rbox(0, b);
 444         if let Some((first, rest)) = elts.split_first() {
 445             op(self, first);
 446             for elt in rest {
 447                 if space_before {
 448                     self.space();
 449                 }
 450                 self.word_space(sep);
 451                 op(self, elt);
 452             }
 453         }
 454         self.end();
 455     }
 456
 457     fn commasep<T, F>(&mut self, b: Breaks, elts: &[T], op: F)
 458     where
 459         F: FnMut(&mut Self, &T),
 460     {
 461         self.strsep(",", false, b, elts, op)
 462     }
 463
 464     fn maybe_print_comment(&mut self, pos: BytePos) {
 465         while let Some(ref cmnt) = self.next_comment() {
 466             if cmnt.pos < pos {
 467                 self.print_comment(cmnt);
 468             } else {
 469                 break;
 470             }
 471         }
 472     }
 473
 474     fn print_comment(&mut self, cmnt: &comments::Comment) {
 475         match cmnt.style {
 476             comments::Mixed => {
 477                 assert_eq!(cmnt.lines.len(), 1);
 478                 self.zerobreak();
 479                 self.word(cmnt.lines[0].clone());
 480                 self.zerobreak()
 481             }
 482             comments::Isolated => {
 483                 self.hardbreak_if_not_bol();
 484                 for line in &cmnt.lines {
 485                     // Don't print empty lines because they will end up as trailing
 486                     // whitespace.
 487                     if !line.is_empty() {
 488                         self.word(line.clone());
 489                     }
 490                     self.hardbreak();
 491                 }
 492             }
 493             comments::Trailing => {
 494                 if !self.is_beginning_of_line() {
 495                     self.word(" ");
 496                 }
 497                 if cmnt.lines.len() == 1 {
 498                     self.word(cmnt.lines[0].clone());
 499                     self.hardbreak()
 500                 } else {
 501                     self.ibox(0);
 502                     for line in &cmnt.lines {
 503                         if !line.is_empty() {
 504                             self.word(line.clone());
 505                         }
 506                         self.hardbreak();
 507                     }
 508                     self.end();
 509                 }
 510             }
 511             comments::BlankLine => {
 512                 // We need to do at least one, possibly two hardbreaks.
 513                 let twice = match self.last_token() {
 514                     pp::Token::String(s) => ";" == s,
 515                     pp::Token::Begin(_) => true,
 516                     pp::Token::End => true,
 517                     _ => false,
 518                 };
 519                 if twice {
 520                     self.hardbreak();
 521                 }
 522                 self.hardbreak();
 523             }
 524         }
 525         if let Some(cm) = self.comments() {
 526             cm.current += 1;
 527         }
 528     }
 529
 530     fn next_comment(&mut self) -> Option<comments::Comment> {
 531         self.comments().as_mut().and_then(|c| c.next())
 532     }
 533
 534     fn print_literal(&mut self, lit: &ast::Lit) {
 535         self.maybe_print_comment(lit.span.lo());
 536         self.word(lit.token.to_string())
 537     }
 538
 539     fn print_string(&mut self, st: &str, style: ast::StrStyle) {
 540         let st = match style {
 541             ast::StrStyle::Cooked => (format!("\"{}\"", st.escape_debug())),
 542             ast::StrStyle::Raw(n) => {
 543                 format!("r{delim}\"{string}\"{delim}", delim = "#".repeat(n as usize), string = st)
 544             }
 545         };
 546         self.word(st)
 547     }
 548
 549     fn print_inner_attributes(&mut self, attrs: &[ast::Attribute]) {
 550         self.print_either_attributes(attrs, ast::AttrStyle::Inner, false, true)
 551     }
 552
 553     fn print_inner_attributes_no_trailing_hardbreak(&mut self, attrs: &[ast::Attribute]) {
 554         self.print_either_attributes(attrs, ast::AttrStyle::Inner, false, false)
 555     }
 556
 557     fn print_outer_attributes(&mut self, attrs: &[ast::Attribute]) {
 558         self.print_either_attributes(attrs, ast::AttrStyle::Outer, false, true)
 559     }
 560
 561     fn print_inner_attributes_inline(&mut self, attrs: &[ast::Attribute]) {
 562         self.print_either_attributes(attrs, ast::AttrStyle::Inner, true, true)
 563     }
 564
 565     fn print_outer_attributes_inline(&mut self, attrs: &[ast::Attribute]) {
 566         self.print_either_attributes(attrs, ast::AttrStyle::Outer, true, true)
 567     }
 568
 569     fn print_either_attributes(
 570         &mut self,
 571         attrs: &[ast::Attribute],
 572         kind: ast::AttrStyle,
 573         is_inline: bool,
 574         trailing_hardbreak: bool,
 575     ) {
 576         let mut count = 0;
 577         for attr in attrs {
 578             if attr.style == kind {
 579                 self.print_attribute_inline(attr, is_inline);
 580                 if is_inline {
 581                     self.nbsp();
 582                 }
 583                 count += 1;
 584             }
 585         }
 586         if count > 0 && trailing_hardbreak && !is_inline {
 587             self.hardbreak_if_not_bol();
 588         }
 589     }
 590
 591     fn print_attribute(&mut self, attr: &ast::Attribute) {
 592         self.print_attribute_inline(attr, false)
 593     }
 594
 595     fn print_attribute_inline(&mut self, attr: &ast::Attribute, is_inline: bool) {
 596         if !is_inline {
 597             self.hardbreak_if_not_bol();
 598         }
 599         self.maybe_print_comment(attr.span.lo());
 600         match attr.kind {
 601             ast::AttrKind::Normal(ref item) => {
 602                 match attr.style {
 603                     ast::AttrStyle::Inner => self.word("#!["),
 604                     ast::AttrStyle::Outer => self.word("#["),
 605                 }
 606                 self.print_attr_item(&item, attr.span);
 607                 self.word("]");
 608             }
 609             ast::AttrKind::DocComment(comment) => {
 610                 self.word(comment.to_string());
 611                 self.hardbreak()
 612             }
 613         }
 614     }
 615
 616     fn print_attr_item(&mut self, item: &ast::AttrItem, span: Span) {
 617         self.ibox(0);
 618         match &item.args {
 619             MacArgs::Delimited(_, delim, tokens) => self.print_mac_common(
 620                 Some(MacHeader::Path(&item.path)),
 621                 false,
 622                 None,
 623                 delim.to_token(),
 624                 tokens.clone(),
 625                 true,
 626                 span,
 627             ),
 628             MacArgs::Empty | MacArgs::Eq(..) => {
 629                 self.print_path(&item.path, false, 0);
 630                 if let MacArgs::Eq(_, tokens) = &item.args {
 631                     self.space();
 632                     self.word_space("=");
 633                     self.print_tts(tokens.clone(), true);
 634                 }
 635             }
 636         }
 637         self.end();
 638     }
 639
 640     fn print_meta_list_item(&mut self, item: &ast::NestedMetaItem) {
 641         match item {
 642             ast::NestedMetaItem::MetaItem(ref mi) => self.print_meta_item(mi),
 643             ast::NestedMetaItem::Literal(ref lit) => self.print_literal(lit),
 644         }
 645     }
 646
 647     fn print_meta_item(&mut self, item: &ast::MetaItem) {
 648         self.ibox(INDENT_UNIT);
 649         match item.kind {
 650             ast::MetaItemKind::Word => self.print_path(&item.path, false, 0),
 651             ast::MetaItemKind::NameValue(ref value) => {
 652                 self.print_path(&item.path, false, 0);
 653                 self.space();
 654                 self.word_space("=");
 655                 self.print_literal(value);
 656             }
 657             ast::MetaItemKind::List(ref items) => {
 658                 self.print_path(&item.path, false, 0);
 659                 self.popen();
 660                 self.commasep(Consistent, &items[..], |s, i| s.print_meta_list_item(i));
 661                 self.pclose();
 662             }
 663         }
 664         self.end();
 665     }
 666
 667     /// This doesn't deserve to be called "pretty" printing, but it should be
 668     /// meaning-preserving. A quick hack that might help would be to look at the
 669     /// spans embedded in the TTs to decide where to put spaces and newlines.
 670     /// But it'd be better to parse these according to the grammar of the
 671     /// appropriate macro, transcribe back into the grammar we just parsed from,
 672     /// and then pretty-print the resulting AST nodes (so, e.g., we print
 673     /// expression arguments as expressions). It can be done! I think.
 674     fn print_tt(&mut self, tt: tokenstream::TokenTree, convert_dollar_crate: bool) {
 675         match tt {
 676             TokenTree::Token(ref token) => {
 677                 self.word(token_to_string_ext(&token, convert_dollar_crate));
 678                 match token.kind {
 679                     token::DocComment(..) => self.hardbreak(),
 680                     _ => {}
 681                 }
 682             }
 683             TokenTree::Delimited(dspan, delim, tts) => {
 684                 self.print_mac_common(
 685                     None,
 686                     false,
 687                     None,
 688                     delim,
 689                     tts,
 690                     convert_dollar_crate,
 691                     dspan.entire(),
 692                 );
 693             }
 694         }
 695     }
 696
 697     fn print_tts(&mut self, tts: tokenstream::TokenStream, convert_dollar_crate: bool) {
 698         for (i, tt) in tts.into_trees().enumerate() {
 699             if i != 0 && tt_prepend_space(&tt) {
 700                 self.space();
 701             }
 702             self.print_tt(tt, convert_dollar_crate);
 703         }
 704     }
 705
 706     fn print_mac_common(
 707         &mut self,
 708         header: Option<MacHeader<'_>>,
 709         has_bang: bool,
 710         ident: Option<ast::Ident>,
 711         delim: DelimToken,
 712         tts: TokenStream,
 713         convert_dollar_crate: bool,
 714         span: Span,
 715     ) {
 716         if delim == DelimToken::Brace {
 717             self.cbox(INDENT_UNIT);
 718         }
 719         match header {
 720             Some(MacHeader::Path(path)) => self.print_path(path, false, 0),
 721             Some(MacHeader::Keyword(kw)) => self.word(kw),
 722             None => {}
 723         }
 724         if has_bang {
 725             self.word("!");
 726         }
 727         if let Some(ident) = ident {
 728             self.nbsp();
 729             self.print_ident(ident);
 730         }
 731         match delim {
 732             DelimToken::Brace => {
 733                 if header.is_some() || has_bang || ident.is_some() {
 734                     self.nbsp();
 735                 }
 736                 self.word("{");
 737                 if !tts.is_empty() {
 738                     self.space();
 739                 }
 740             }
 741             _ => self.word(token_kind_to_string(&token::OpenDelim(delim))),
 742         }
 743         self.ibox(0);
 744         self.print_tts(tts, convert_dollar_crate);
 745         self.end();
 746         match delim {
 747             DelimToken::Brace => self.bclose(span),
 748             _ => self.word(token_kind_to_string(&token::CloseDelim(delim))),
 749         }
 750     }
 751
 752     fn print_path(&mut self, path: &ast::Path, colons_before_params: bool, depth: usize) {
 753         self.maybe_print_comment(path.span.lo());
 754
 755         for (i, segment) in path.segments[..path.segments.len() - depth].iter().enumerate() {
 756             if i > 0 {
 757                 self.word("::")
 758             }
 759             self.print_path_segment(segment, colons_before_params);
 760         }
 761     }
 762
 763     fn print_path_segment(&mut self, segment: &ast::PathSegment, colons_before_params: bool) {
 764         if segment.ident.name != kw::PathRoot {
 765             self.print_ident(segment.ident);
 766             if let Some(ref args) = segment.args {
 767                 self.print_generic_args(args, colons_before_params);
 768             }
 769         }
 770     }
 771
 772     fn head<S: Into<Cow<'static, str>>>(&mut self, w: S) {
 773         let w = w.into();
 774         // Outer-box is consistent.
 775         self.cbox(INDENT_UNIT);
 776         // Head-box is inconsistent.
 777         self.ibox(w.len() + 1);
 778         // Keyword that starts the head.
 779         if !w.is_empty() {
 780             self.word_nbsp(w);
 781         }
 782     }
 783
 784     fn bopen(&mut self) {
 785         self.word("{");
 786         self.end(); // Close the head-box.
 787     }
 788
 789     fn bclose_maybe_open(&mut self, span: rustc_span::Span, close_box: bool) {
 790         self.maybe_print_comment(span.hi());
 791         self.break_offset_if_not_bol(1, -(INDENT_UNIT as isize));
 792         self.word("}");
 793         if close_box {
 794             self.end(); // Close the outer-box.
 795         }
 796     }
 797
 798     fn bclose(&mut self, span: rustc_span::Span) {
 799         self.bclose_maybe_open(span, true)
 800     }
 801
 802     fn break_offset_if_not_bol(&mut self, n: usize, off: isize) {
 803         if !self.is_beginning_of_line() {
 804             self.break_offset(n, off)
 805         } else {
 806             if off != 0 && self.last_token().is_hardbreak_tok() {
 807                 // We do something pretty sketchy here: tuck the nonzero
 808                 // offset-adjustment we were going to deposit along with the
 809                 // break into the previous hardbreak.
 810                 self.replace_last_token(pp::Printer::hardbreak_tok_offset(off));
 811             }
 812         }
 813     }
 814 }
 815
 816 impl<'a> PrintState<'a> for State<'a> {
 817     fn comments(&mut self) -> &mut Option<Comments<'a>> {
 818         &mut self.comments
 819     }
 820
 821     fn print_ident(&mut self, ident: ast::Ident) {
 822         self.s.word(ast_ident_to_string(ident, ident.is_raw_guess()));
 823         self.ann.post(self, AnnNode::Ident(&ident))
 824     }
 825
 826     fn print_generic_args(&mut self, args: &ast::GenericArgs, colons_before_params: bool) {
 827         if colons_before_params {
 828             self.s.word("::")
 829         }
 830
 831         match *args {
 832             ast::GenericArgs::AngleBracketed(ref data) => {
 833                 self.s.word("<");
 834
 835                 self.commasep(Inconsistent, &data.args, |s, generic_arg| {
 836                     s.print_generic_arg(generic_arg)
 837                 });
 838
 839                 let mut comma = data.args.len() != 0;
 840
 841                 for constraint in data.constraints.iter() {
 842                     if comma {
 843                         self.word_space(",")
 844                     }
 845                     self.print_ident(constraint.ident);
 846                     self.s.space();
 847                     match constraint.kind {
 848                         ast::AssocTyConstraintKind::Equality { ref ty } => {
 849                             self.word_space("=");
 850                             self.print_type(ty);
 851                         }
 852                         ast::AssocTyConstraintKind::Bound { ref bounds } => {
 853                             self.print_type_bounds(":", &*bounds);
 854                         }
 855                     }
 856                     comma = true;
 857                 }
 858
 859                 self.s.word(">")
 860             }
 861
 862             ast::GenericArgs::Parenthesized(ref data) => {
 863                 self.s.word("(");
 864                 self.commasep(Inconsistent, &data.inputs, |s, ty| s.print_type(ty));
 865                 self.s.word(")");
 866                 self.print_fn_ret_ty(&data.output);
 867             }
 868         }
 869     }
 870 }
 871
 872 impl<'a> State<'a> {
 873     // Synthesizes a comment that was not textually present in the original source
 874     // file.
 875     pub fn synth_comment(&mut self, text: String) {
 876         self.s.word("/*");
 877         self.s.space();
 878         self.s.word(text);
 879         self.s.space();
 880         self.s.word("*/")
 881     }
 882
 883     crate fn commasep_cmnt<T, F, G>(&mut self, b: Breaks, elts: &[T], mut op: F, mut get_span: G)
 884     where
 885         F: FnMut(&mut State<'_>, &T),
 886         G: FnMut(&T) -> rustc_span::Span,
 887     {
 888         self.rbox(0, b);
 889         let len = elts.len();
 890         let mut i = 0;
 891         for elt in elts {
 892             self.maybe_print_comment(get_span(elt).hi());
 893             op(self, elt);
 894             i += 1;
 895             if i < len {
 896                 self.s.word(",");
 897                 self.maybe_print_trailing_comment(get_span(elt), Some(get_span(&elts[i]).hi()));
 898                 self.space_if_not_bol();
 899             }
 900         }
 901         self.end();
 902     }
 903
 904     crate fn commasep_exprs(&mut self, b: Breaks, exprs: &[P<ast::Expr>]) {
 905         self.commasep_cmnt(b, exprs, |s, e| s.print_expr(e), |e| e.span)
 906     }
 907
 908     pub fn print_mod(&mut self, _mod: &ast::Mod, attrs: &[ast::Attribute]) {
 909         self.print_inner_attributes(attrs);
 910         for item in &_mod.items {
 911             self.print_item(item);
 912         }
 913     }
 914
 915     crate fn print_foreign_mod(&mut self, nmod: &ast::ForeignMod, attrs: &[ast::Attribute]) {
 916         self.print_inner_attributes(attrs);
 917         for item in &nmod.items {
 918             self.print_foreign_item(item);
 919         }
 920     }
 921
 922     pub fn print_opt_lifetime(&mut self, lifetime: &Option<ast::Lifetime>) {
 923         if let Some(lt) = *lifetime {
 924             self.print_lifetime(lt);
 925             self.nbsp();
 926         }
 927     }
 928
 929     crate fn print_generic_arg(&mut self, generic_arg: &GenericArg) {
 930         match generic_arg {
 931             GenericArg::Lifetime(lt) => self.print_lifetime(*lt),
 932             GenericArg::Type(ty) => self.print_type(ty),
 933             GenericArg::Const(ct) => self.print_expr(&ct.value),
 934         }
 935     }
 936
 937     pub fn print_type(&mut self, ty: &ast::Ty) {
 938         self.maybe_print_comment(ty.span.lo());
 939         self.ibox(0);
 940         match ty.kind {
 941             ast::TyKind::Slice(ref ty) => {
 942                 self.s.word("[");
 943                 self.print_type(ty);
 944                 self.s.word("]");
 945             }
 946             ast::TyKind::Ptr(ref mt) => {
 947                 self.s.word("*");
 948                 self.print_mt(mt, true);
 949             }
 950             ast::TyKind::Rptr(ref lifetime, ref mt) => {
 951                 self.s.word("&");
 952                 self.print_opt_lifetime(lifetime);
 953                 self.print_mt(mt, false);
 954             }
 955             ast::TyKind::Never => {
 956                 self.s.word("!");
 957             }
 958             ast::TyKind::Tup(ref elts) => {
 959                 self.popen();
 960                 self.commasep(Inconsistent, &elts[..], |s, ty| s.print_type(ty));
 961                 if elts.len() == 1 {
 962                     self.s.word(",");
 963                 }
 964                 self.pclose();
 965             }
 966             ast::TyKind::Paren(ref typ) => {
 967                 self.popen();
 968                 self.print_type(typ);
 969                 self.pclose();
 970             }
 971             ast::TyKind::BareFn(ref f) => {
 972                 self.print_ty_fn(f.ext, f.unsafety, &f.decl, None, &f.generic_params);
 973             }
 974             ast::TyKind::Path(None, ref path) => {
 975                 self.print_path(path, false, 0);
 976             }
 977             ast::TyKind::Path(Some(ref qself), ref path) => self.print_qpath(path, qself, false),
 978             ast::TyKind::TraitObject(ref bounds, syntax) => {
 979                 let prefix = if syntax == ast::TraitObjectSyntax::Dyn { "dyn" } else { "" };
 980                 self.print_type_bounds(prefix, &bounds[..]);
 981             }
 982             ast::TyKind::ImplTrait(_, ref bounds) => {
 983                 self.print_type_bounds("impl", &bounds[..]);
 984             }
 985             ast::TyKind::Array(ref ty, ref length) => {
 986                 self.s.word("[");
 987                 self.print_type(ty);
 988                 self.s.word("; ");
 989                 self.print_expr(&length.value);
 990                 self.s.word("]");
 991             }
 992             ast::TyKind::Typeof(ref e) => {
 993                 self.s.word("typeof(");
 994                 self.print_expr(&e.value);
 995                 self.s.word(")");
 996             }
 997             ast::TyKind::Infer => {
 998                 self.s.word("_");
 999             }
1000             ast::TyKind::Err => {
1001                 self.popen();
1002                 self.s.word("/*ERROR*/");
1003                 self.pclose();
1004             }
1005             ast::TyKind::ImplicitSelf => {
1006                 self.s.word("Self");
1007             }
1008             ast::TyKind::Mac(ref m) => {
1009                 self.print_mac(m);
1010             }
1011             ast::TyKind::CVarArgs => {
1012                 self.s.word("...");
1013             }
1014         }
1015         self.end();
1016     }
1017
1018     crate fn print_foreign_item(&mut self, item: &ast::ForeignItem) {
1019         self.hardbreak_if_not_bol();
1020         self.maybe_print_comment(item.span.lo());
1021         self.print_outer_attributes(&item.attrs);
1022         match item.kind {
1023             ast::ForeignItemKind::Fn(ref sig, ref gen, ref body) => {
1024                 self.print_fn_full(sig, item.ident, gen, &item.vis, body.as_deref(), &item.attrs);
1025             }
1026             ast::ForeignItemKind::Static(ref t, m) => {
1027                 self.head(visibility_qualified(&item.vis, "static"));
1028                 if m == ast::Mutability::Mut {
1029                     self.word_space("mut");
1030                 }
1031                 self.print_ident(item.ident);
1032                 self.word_space(":");
1033                 self.print_type(t);
1034                 self.s.word(";");
1035                 self.end(); // end the head-ibox
1036                 self.end(); // end the outer cbox
1037             }
1038             ast::ForeignItemKind::Ty => {
1039                 self.head(visibility_qualified(&item.vis, "type"));
1040                 self.print_ident(item.ident);
1041                 self.s.word(";");
1042                 self.end(); // end the head-ibox
1043                 self.end(); // end the outer cbox
1044             }
1045             ast::ForeignItemKind::Macro(ref m) => {
1046                 self.print_mac(m);
1047                 if m.args.need_semicolon() {
1048                     self.s.word(";");
1049                 }
1050             }
1051         }
1052     }
1053
1054     fn print_associated_const(
1055         &mut self,
1056         ident: ast::Ident,
1057         ty: &ast::Ty,
1058         default: Option<&ast::Expr>,
1059         vis: &ast::Visibility,
1060     ) {
1061         self.s.word(visibility_qualified(vis, ""));
1062         self.word_space("const");
1063         self.print_ident(ident);
1064         self.word_space(":");
1065         self.print_type(ty);
1066         if let Some(expr) = default {
1067             self.s.space();
1068             self.word_space("=");
1069             self.print_expr(expr);
1070         }
1071         self.s.word(";")
1072     }
1073
1074     fn print_associated_type(
1075         &mut self,
1076         ident: ast::Ident,
1077         generics: &ast::Generics,
1078         bounds: &ast::GenericBounds,
1079         ty: Option<&ast::Ty>,
1080     ) {
1081         self.word_space("type");
1082         self.print_ident(ident);
1083         self.print_generic_params(&generics.params);
1084         self.print_type_bounds(":", bounds);
1085         self.print_where_clause(&generics.where_clause);
1086         if let Some(ty) = ty {
1087             self.s.space();
1088             self.word_space("=");
1089             self.print_type(ty);
1090         }
1091         self.s.word(";")
1092     }
1093
1094     /// Pretty-prints an item.
1095     crate fn print_item(&mut self, item: &ast::Item) {
1096         self.hardbreak_if_not_bol();
1097         self.maybe_print_comment(item.span.lo());
1098         self.print_outer_attributes(&item.attrs);
1099         self.ann.pre(self, AnnNode::Item(item));
1100         match item.kind {
1101             ast::ItemKind::ExternCrate(orig_name) => {
1102                 self.head(visibility_qualified(&item.vis, "extern crate"));
1103                 if let Some(orig_name) = orig_name {
1104                     self.print_name(orig_name);
1105                     self.s.space();
1106                     self.s.word("as");
1107                     self.s.space();
1108                 }
1109                 self.print_ident(item.ident);
1110                 self.s.word(";");
1111                 self.end(); // end inner head-block
1112                 self.end(); // end outer head-block
1113             }
1114             ast::ItemKind::Use(ref tree) => {
1115                 self.head(visibility_qualified(&item.vis, "use"));
1116                 self.print_use_tree(tree);
1117                 self.s.word(";");
1118                 self.end(); // end inner head-block
1119                 self.end(); // end outer head-block
1120             }
1121             ast::ItemKind::Static(ref ty, m, ref expr) => {
1122                 self.head(visibility_qualified(&item.vis, "static"));
1123                 if m == ast::Mutability::Mut {
1124                     self.word_space("mut");
1125                 }
1126                 self.print_ident(item.ident);
1127                 self.word_space(":");
1128                 self.print_type(ty);
1129                 self.s.space();
1130                 self.end(); // end the head-ibox
1131
1132                 self.word_space("=");
1133                 self.print_expr(expr);
1134                 self.s.word(";");
1135                 self.end(); // end the outer cbox
1136             }
1137             ast::ItemKind::Const(ref ty, ref expr) => {
1138                 self.head(visibility_qualified(&item.vis, "const"));
1139                 self.print_ident(item.ident);
1140                 self.word_space(":");
1141                 self.print_type(ty);
1142                 self.s.space();
1143                 self.end(); // end the head-ibox
1144
1145                 self.word_space("=");
1146                 self.print_expr(expr);
1147                 self.s.word(";");
1148                 self.end(); // end the outer cbox
1149             }
1150             ast::ItemKind::Fn(ref sig, ref gen, ref body) => {
1151                 self.print_fn_full(sig, item.ident, gen, &item.vis, body.as_deref(), &item.attrs);
1152             }
1153             ast::ItemKind::Mod(ref _mod) => {
1154                 self.head(visibility_qualified(&item.vis, "mod"));
1155                 self.print_ident(item.ident);
1156
1157                 if _mod.inline || self.is_expanded {
1158                     self.nbsp();
1159                     self.bopen();
1160                     self.print_mod(_mod, &item.attrs);
1161                     self.bclose(item.span);
1162                 } else {
1163                     self.s.word(";");
1164                     self.end(); // end inner head-block
1165                     self.end(); // end outer head-block
1166                 }
1167             }
1168             ast::ItemKind::ForeignMod(ref nmod) => {
1169                 self.head("extern");
1170                 if let Some(abi) = nmod.abi {
1171                     self.print_literal(&abi.as_lit());
1172                     self.nbsp();
1173                 }
1174                 self.bopen();
1175                 self.print_foreign_mod(nmod, &item.attrs);
1176                 self.bclose(item.span);
1177             }
1178             ast::ItemKind::GlobalAsm(ref ga) => {
1179                 self.head(visibility_qualified(&item.vis, "global_asm!"));
1180                 self.s.word(ga.asm.to_string());
1181                 self.end();
1182             }
1183             ast::ItemKind::TyAlias(ref ty, ref generics) => {
1184                 self.head(visibility_qualified(&item.vis, "type"));
1185                 self.print_ident(item.ident);
1186                 self.print_generic_params(&generics.params);
1187                 self.end(); // end the inner ibox
1188
1189                 self.print_where_clause(&generics.where_clause);
1190                 self.s.space();
1191                 self.word_space("=");
1192                 self.print_type(ty);
1193                 self.s.word(";");
1194                 self.end(); // end the outer ibox
1195             }
1196             ast::ItemKind::Enum(ref enum_definition, ref params) => {
1197                 self.print_enum_def(enum_definition, params, item.ident, item.span, &item.vis);
1198             }
1199             ast::ItemKind::Struct(ref struct_def, ref generics) => {
1200                 self.head(visibility_qualified(&item.vis, "struct"));
1201                 self.print_struct(struct_def, generics, item.ident, item.span, true);
1202             }
1203             ast::ItemKind::Union(ref struct_def, ref generics) => {
1204                 self.head(visibility_qualified(&item.vis, "union"));
1205                 self.print_struct(struct_def, generics, item.ident, item.span, true);
1206             }
1207             ast::ItemKind::Impl {
1208                 unsafety,
1209                 polarity,
1210                 defaultness,
1211                 constness,
1212                 ref generics,
1213                 ref of_trait,
1214                 ref self_ty,
1215                 ref items,
1216             } => {
1217                 self.head("");
1218                 self.print_visibility(&item.vis);
1219                 self.print_defaultness(defaultness);
1220                 self.print_unsafety(unsafety);
1221                 self.word_nbsp("impl");
1222                 self.print_constness(constness);
1223
1224                 if !generics.params.is_empty() {
1225                     self.print_generic_params(&generics.params);
1226                     self.s.space();
1227                 }
1228
1229                 if polarity == ast::ImplPolarity::Negative {
1230                     self.s.word("!");
1231                 }
1232
1233                 if let Some(ref t) = *of_trait {
1234                     self.print_trait_ref(t);
1235                     self.s.space();
1236                     self.word_space("for");
1237                 }
1238
1239                 self.print_type(self_ty);
1240                 self.print_where_clause(&generics.where_clause);
1241
1242                 self.s.space();
1243                 self.bopen();
1244                 self.print_inner_attributes(&item.attrs);
1245                 for impl_item in items {
1246                     self.print_assoc_item(impl_item);
1247                 }
1248                 self.bclose(item.span);
1249             }
1250             ast::ItemKind::Trait(is_auto, unsafety, ref generics, ref bounds, ref trait_items) => {
1251                 self.head("");
1252                 self.print_visibility(&item.vis);
1253                 self.print_unsafety(unsafety);
1254                 self.print_is_auto(is_auto);
1255                 self.word_nbsp("trait");
1256                 self.print_ident(item.ident);
1257                 self.print_generic_params(&generics.params);
1258                 let mut real_bounds = Vec::with_capacity(bounds.len());
1259                 for b in bounds.iter() {
1260                     if let GenericBound::Trait(ref ptr, ast::TraitBoundModifier::Maybe) = *b {
1261                         self.s.space();
1262                         self.word_space("for ?");
1263                         self.print_trait_ref(&ptr.trait_ref);
1264                     } else {
1265                         real_bounds.push(b.clone());
1266                     }
1267                 }
1268                 self.print_type_bounds(":", &real_bounds[..]);
1269                 self.print_where_clause(&generics.where_clause);
1270                 self.s.word(" ");
1271                 self.bopen();
1272                 self.print_inner_attributes(&item.attrs);
1273                 for trait_item in trait_items {
1274                     self.print_assoc_item(trait_item);
1275                 }
1276                 self.bclose(item.span);
1277             }
1278             ast::ItemKind::TraitAlias(ref generics, ref bounds) => {
1279                 self.head("");
1280                 self.print_visibility(&item.vis);
1281                 self.word_nbsp("trait");
1282                 self.print_ident(item.ident);
1283                 self.print_generic_params(&generics.params);
1284                 let mut real_bounds = Vec::with_capacity(bounds.len());
1285                 // FIXME(durka) this seems to be some quite outdated syntax
1286                 for b in bounds.iter() {
1287                     if let GenericBound::Trait(ref ptr, ast::TraitBoundModifier::Maybe) = *b {
1288                         self.s.space();
1289                         self.word_space("for ?");
1290                         self.print_trait_ref(&ptr.trait_ref);
1291                     } else {
1292                         real_bounds.push(b.clone());
1293                     }
1294                 }
1295                 self.nbsp();
1296                 self.print_type_bounds("=", &real_bounds[..]);
1297                 self.print_where_clause(&generics.where_clause);
1298                 self.s.word(";");
1299             }
1300             ast::ItemKind::Mac(ref mac) => {
1301                 self.print_mac(mac);
1302                 if mac.args.need_semicolon() {
1303                     self.s.word(";");
1304                 }
1305             }
1306             ast::ItemKind::MacroDef(ref macro_def) => {
1307                 let (kw, has_bang) = if macro_def.legacy {
1308                     ("macro_rules", true)
1309                 } else {
1310                     self.print_visibility(&item.vis);
1311                     ("macro", false)
1312                 };
1313                 self.print_mac_common(
1314                     Some(MacHeader::Keyword(kw)),
1315                     has_bang,
1316                     Some(item.ident),
1317                     macro_def.body.delim(),
1318                     macro_def.body.inner_tokens(),
1319                     true,
1320                     item.span,
1321                 );
1322             }
1323         }
1324         self.ann.post(self, AnnNode::Item(item))
1325     }
1326
1327     fn print_trait_ref(&mut self, t: &ast::TraitRef) {
1328         self.print_path(&t.path, false, 0)
1329     }
1330
1331     fn print_formal_generic_params(&mut self, generic_params: &[ast::GenericParam]) {
1332         if !generic_params.is_empty() {
1333             self.s.word("for");
1334             self.print_generic_params(generic_params);
1335             self.nbsp();
1336         }
1337     }
1338
1339     fn print_poly_trait_ref(&mut self, t: &ast::PolyTraitRef) {
1340         self.print_formal_generic_params(&t.bound_generic_params);
1341         self.print_trait_ref(&t.trait_ref)
1342     }
1343
1344     crate fn print_enum_def(
1345         &mut self,
1346         enum_definition: &ast::EnumDef,
1347         generics: &ast::Generics,
1348         ident: ast::Ident,
1349         span: rustc_span::Span,
1350         visibility: &ast::Visibility,
1351     ) {
1352         self.head(visibility_qualified(visibility, "enum"));
1353         self.print_ident(ident);
1354         self.print_generic_params(&generics.params);
1355         self.print_where_clause(&generics.where_clause);
1356         self.s.space();
1357         self.print_variants(&enum_definition.variants, span)
1358     }
1359
1360     crate fn print_variants(&mut self, variants: &[ast::Variant], span: rustc_span::Span) {
1361         self.bopen();
1362         for v in variants {
1363             self.space_if_not_bol();
1364             self.maybe_print_comment(v.span.lo());
1365             self.print_outer_attributes(&v.attrs);
1366             self.ibox(INDENT_UNIT);
1367             self.print_variant(v);
1368             self.s.word(",");
1369             self.end();
1370             self.maybe_print_trailing_comment(v.span, None);
1371         }
1372         self.bclose(span)
1373     }
1374
1375     crate fn print_visibility(&mut self, vis: &ast::Visibility) {
1376         match vis.node {
1377             ast::VisibilityKind::Public => self.word_nbsp("pub"),
1378             ast::VisibilityKind::Crate(sugar) => match sugar {
1379                 ast::CrateSugar::PubCrate => self.word_nbsp("pub(crate)"),
1380                 ast::CrateSugar::JustCrate => self.word_nbsp("crate"),
1381             },
1382             ast::VisibilityKind::Restricted { ref path, .. } => {
1383                 let path = to_string(|s| s.print_path(path, false, 0));
1384                 if path == "self" || path == "super" {
1385                     self.word_nbsp(format!("pub({})", path))
1386                 } else {
1387                     self.word_nbsp(format!("pub(in {})", path))
1388                 }
1389             }
1390             ast::VisibilityKind::Inherited => {}
1391         }
1392     }
1393
1394     crate fn print_defaultness(&mut self, defaultness: ast::Defaultness) {
1395         if let ast::Defaultness::Default = defaultness {
1396             self.word_nbsp("default");
1397         }
1398     }
1399
1400     crate fn print_struct(
1401         &mut self,
1402         struct_def: &ast::VariantData,
1403         generics: &ast::Generics,
1404         ident: ast::Ident,
1405         span: rustc_span::Span,
1406         print_finalizer: bool,
1407     ) {
1408         self.print_ident(ident);
1409         self.print_generic_params(&generics.params);
1410         match struct_def {
1411             ast::VariantData::Tuple(..) | ast::VariantData::Unit(..) => {
1412                 if let ast::VariantData::Tuple(..) = struct_def {
1413                     self.popen();
1414                     self.commasep(Inconsistent, struct_def.fields(), |s, field| {
1415                         s.maybe_print_comment(field.span.lo());
1416                         s.print_outer_attributes(&field.attrs);
1417                         s.print_visibility(&field.vis);
1418                         s.print_type(&field.ty)
1419                     });
1420                     self.pclose();
1421                 }
1422                 self.print_where_clause(&generics.where_clause);
1423                 if print_finalizer {
1424                     self.s.word(";");
1425                 }
1426                 self.end();
1427                 self.end(); // Close the outer-box.
1428             }
1429             ast::VariantData::Struct(..) => {
1430                 self.print_where_clause(&generics.where_clause);
1431                 self.nbsp();
1432                 self.bopen();
1433                 self.hardbreak_if_not_bol();
1434
1435                 for field in struct_def.fields() {
1436                     self.hardbreak_if_not_bol();
1437                     self.maybe_print_comment(field.span.lo());
1438                     self.print_outer_attributes(&field.attrs);
1439                     self.print_visibility(&field.vis);
1440                     self.print_ident(field.ident.unwrap());
1441                     self.word_nbsp(":");
1442                     self.print_type(&field.ty);
1443                     self.s.word(",");
1444                 }
1445
1446                 self.bclose(span)
1447             }
1448         }
1449     }
1450
1451     crate fn print_variant(&mut self, v: &ast::Variant) {
1452         self.head("");
1453         self.print_visibility(&v.vis);
1454         let generics = ast::Generics::default();
1455         self.print_struct(&v.data, &generics, v.ident, v.span, false);
1456         match v.disr_expr {
1457             Some(ref d) => {
1458                 self.s.space();
1459                 self.word_space("=");
1460                 self.print_expr(&d.value)
1461             }
1462             _ => {}
1463         }
1464     }
1465
1466     crate fn print_assoc_item(&mut self, item: &ast::AssocItem) {
1467         self.ann.pre(self, AnnNode::SubItem(item.id));
1468         self.hardbreak_if_not_bol();
1469         self.maybe_print_comment(item.span.lo());
1470         self.print_outer_attributes(&item.attrs);
1471         self.print_defaultness(item.defaultness);
1472         match &item.kind {
1473             ast::AssocItemKind::Const(ty, expr) => {
1474                 self.print_associated_const(item.ident, ty, expr.as_deref(), &item.vis);
1475             }
1476             ast::AssocItemKind::Fn(sig, generics, body) => {
1477                 let body = body.as_deref();
1478                 self.print_fn_full(sig, item.ident, generics, &item.vis, body, &item.attrs);
1479             }
1480             ast::AssocItemKind::TyAlias(generics, bounds, ty) => {
1481                 self.print_associated_type(item.ident, generics, bounds, ty.as_deref());
1482             }
1483             ast::AssocItemKind::Macro(mac) => {
1484                 self.print_mac(mac);
1485                 if mac.args.need_semicolon() {
1486                     self.s.word(";");
1487                 }
1488             }
1489         }
1490         self.ann.post(self, AnnNode::SubItem(item.id))
1491     }
1492
1493     crate fn print_stmt(&mut self, st: &ast::Stmt) {
1494         self.maybe_print_comment(st.span.lo());
1495         match st.kind {
1496             ast::StmtKind::Local(ref loc) => {
1497                 self.print_outer_attributes(&loc.attrs);
1498                 self.space_if_not_bol();
1499                 self.ibox(INDENT_UNIT);
1500                 self.word_nbsp("let");
1501
1502                 self.ibox(INDENT_UNIT);
1503                 self.print_local_decl(loc);
1504                 self.end();
1505                 if let Some(ref init) = loc.init {
1506                     self.nbsp();
1507                     self.word_space("=");
1508                     self.print_expr(init);
1509                 }
1510                 self.s.word(";");
1511                 self.end();
1512             }
1513             ast::StmtKind::Item(ref item) => self.print_item(item),
1514             ast::StmtKind::Expr(ref expr) => {
1515                 self.space_if_not_bol();
1516                 self.print_expr_outer_attr_style(expr, false);
1517                 if classify::expr_requires_semi_to_be_stmt(expr) {
1518                     self.s.word(";");
1519                 }
1520             }
1521             ast::StmtKind::Semi(ref expr) => {
1522                 match expr.kind {
1523                     // Filter out empty `Tup` exprs created for the `redundant_semicolon`
1524                     // lint, as they shouldn't be visible and interact poorly
1525                     // with proc macros.
1526                     ast::ExprKind::Tup(ref exprs) if exprs.is_empty() && expr.attrs.is_empty() => {
1527                         ()
1528                     }
1529                     _ => {
1530                         self.space_if_not_bol();
1531                         self.print_expr_outer_attr_style(expr, false);
1532                         self.s.word(";");
1533                     }
1534                 }
1535             }
1536             ast::StmtKind::Mac(ref mac) => {
1537                 let (ref mac, style, ref attrs) = **mac;
1538                 self.space_if_not_bol();
1539                 self.print_outer_attributes(attrs);
1540                 self.print_mac(mac);
1541                 if style == ast::MacStmtStyle::Semicolon {
1542                     self.s.word(";");
1543                 }
1544             }
1545         }
1546         self.maybe_print_trailing_comment(st.span, None)
1547     }
1548
1549     crate fn print_block(&mut self, blk: &ast::Block) {
1550         self.print_block_with_attrs(blk, &[])
1551     }
1552
1553     crate fn print_block_unclosed_indent(&mut self, blk: &ast::Block) {
1554         self.print_block_maybe_unclosed(blk, &[], false)
1555     }
1556
1557     crate fn print_block_with_attrs(&mut self, blk: &ast::Block, attrs: &[ast::Attribute]) {
1558         self.print_block_maybe_unclosed(blk, attrs, true)
1559     }
1560
1561     crate fn print_block_maybe_unclosed(
1562         &mut self,
1563         blk: &ast::Block,
1564         attrs: &[ast::Attribute],
1565         close_box: bool,
1566     ) {
1567         match blk.rules {
1568             BlockCheckMode::Unsafe(..) => self.word_space("unsafe"),
1569             BlockCheckMode::Default => (),
1570         }
1571         self.maybe_print_comment(blk.span.lo());
1572         self.ann.pre(self, AnnNode::Block(blk));
1573         self.bopen();
1574
1575         self.print_inner_attributes(attrs);
1576
1577         for (i, st) in blk.stmts.iter().enumerate() {
1578             match st.kind {
1579                 ast::StmtKind::Expr(ref expr) if i == blk.stmts.len() - 1 => {
1580                     self.maybe_print_comment(st.span.lo());
1581                     self.space_if_not_bol();
1582                     self.print_expr_outer_attr_style(expr, false);
1583                     self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi()));
1584                 }
1585                 _ => self.print_stmt(st),
1586             }
1587         }
1588
1589         self.bclose_maybe_open(blk.span, close_box);
1590         self.ann.post(self, AnnNode::Block(blk))
1591     }
1592
1593     /// Print a `let pat = scrutinee` expression.
1594     crate fn print_let(&mut self, pat: &ast::Pat, scrutinee: &ast::Expr) {
1595         self.s.word("let ");
1596
1597         self.print_pat(pat);
1598         self.s.space();
1599
1600         self.word_space("=");
1601         self.print_expr_cond_paren(
1602             scrutinee,
1603             Self::cond_needs_par(scrutinee)
1604                 || parser::needs_par_as_let_scrutinee(scrutinee.precedence().order()),
1605         )
1606     }
1607
1608     fn print_else(&mut self, els: Option<&ast::Expr>) {
1609         if let Some(_else) = els {
1610             match _else.kind {
1611                 // Another `else if` block.
1612                 ast::ExprKind::If(ref i, ref then, ref e) => {
1613                     self.cbox(INDENT_UNIT - 1);
1614                     self.ibox(0);
1615                     self.s.word(" else if ");
1616                     self.print_expr_as_cond(i);
1617                     self.s.space();
1618                     self.print_block(then);
1619                     self.print_else(e.as_deref())
1620                 }
1621                 // Final `else` block.
1622                 ast::ExprKind::Block(ref b, _) => {
1623                     self.cbox(INDENT_UNIT - 1);
1624                     self.ibox(0);
1625                     self.s.word(" else ");
1626                     self.print_block(b)
1627                 }
1628                 // Constraints would be great here!
1629                 _ => {
1630                     panic!("print_if saw if with weird alternative");
1631                 }
1632             }
1633         }
1634     }
1635
1636     crate fn print_if(&mut self, test: &ast::Expr, blk: &ast::Block, elseopt: Option<&ast::Expr>) {
1637         self.head("if");
1638
1639         self.print_expr_as_cond(test);
1640         self.s.space();
1641
1642         self.print_block(blk);
1643         self.print_else(elseopt)
1644     }
1645
1646     crate fn print_mac(&mut self, m: &ast::Mac) {
1647         self.print_mac_common(
1648             Some(MacHeader::Path(&m.path)),
1649             true,
1650             None,
1651             m.args.delim(),
1652             m.args.inner_tokens(),
1653             true,
1654             m.span(),
1655         );
1656     }
1657
1658     fn print_call_post(&mut self, args: &[P<ast::Expr>]) {
1659         self.popen();
1660         self.commasep_exprs(Inconsistent, args);
1661         self.pclose()
1662     }
1663
1664     crate fn print_expr_maybe_paren(&mut self, expr: &ast::Expr, prec: i8) {
1665         self.print_expr_cond_paren(expr, expr.precedence().order() < prec)
1666     }
1667
1668     /// Prints an expr using syntax that's acceptable in a condition position, such as the `cond` in
1669     /// `if cond { ... }`.
1670     crate fn print_expr_as_cond(&mut self, expr: &ast::Expr) {
1671         self.print_expr_cond_paren(expr, Self::cond_needs_par(expr))
1672     }
1673
1674     /// Does `expr` need parenthesis when printed in a condition position?
1675     fn cond_needs_par(expr: &ast::Expr) -> bool {
1676         match expr.kind {
1677             // These cases need parens due to the parse error observed in #26461: `if return {}`
1678             // parses as the erroneous construct `if (return {})`, not `if (return) {}`.
1679             ast::ExprKind::Closure(..) | ast::ExprKind::Ret(..) | ast::ExprKind::Break(..) => true,
1680
1681             _ => parser::contains_exterior_struct_lit(expr),
1682         }
1683     }
1684
1685     /// Prints `expr` or `(expr)` when `needs_par` holds.
1686     fn print_expr_cond_paren(&mut self, expr: &ast::Expr, needs_par: bool) {
1687         if needs_par {
1688             self.popen();
1689         }
1690         self.print_expr(expr);
1691         if needs_par {
1692             self.pclose();
1693         }
1694     }
1695
1696     fn print_expr_vec(&mut self, exprs: &[P<ast::Expr>], attrs: &[Attribute]) {
1697         self.ibox(INDENT_UNIT);
1698         self.s.word("[");
1699         self.print_inner_attributes_inline(attrs);
1700         self.commasep_exprs(Inconsistent, &exprs[..]);
1701         self.s.word("]");
1702         self.end();
1703     }
1704
1705     fn print_expr_repeat(
1706         &mut self,
1707         element: &ast::Expr,
1708         count: &ast::AnonConst,
1709         attrs: &[Attribute],
1710     ) {
1711         self.ibox(INDENT_UNIT);
1712         self.s.word("[");
1713         self.print_inner_attributes_inline(attrs);
1714         self.print_expr(element);
1715         self.word_space(";");
1716         self.print_expr(&count.value);
1717         self.s.word("]");
1718         self.end();
1719     }
1720
1721     fn print_expr_struct(
1722         &mut self,
1723         path: &ast::Path,
1724         fields: &[ast::Field],
1725         wth: &Option<P<ast::Expr>>,
1726         attrs: &[Attribute],
1727     ) {
1728         self.print_path(path, true, 0);
1729         self.s.word("{");
1730         self.print_inner_attributes_inline(attrs);
1731         self.commasep_cmnt(
1732             Consistent,
1733             &fields[..],
1734             |s, field| {
1735                 s.print_outer_attributes(&field.attrs);
1736                 s.ibox(INDENT_UNIT);
1737                 if !field.is_shorthand {
1738                     s.print_ident(field.ident);
1739                     s.word_space(":");
1740                 }
1741                 s.print_expr(&field.expr);
1742                 s.end();
1743             },
1744             |f| f.span,
1745         );
1746         match *wth {
1747             Some(ref expr) => {
1748                 self.ibox(INDENT_UNIT);
1749                 if !fields.is_empty() {
1750                     self.s.word(",");
1751                     self.s.space();
1752                 }
1753                 self.s.word("..");
1754                 self.print_expr(expr);
1755                 self.end();
1756             }
1757             _ => {
1758                 if !fields.is_empty() {
1759                     self.s.word(",")
1760                 }
1761             }
1762         }
1763         self.s.word("}");
1764     }
1765
1766     fn print_expr_tup(&mut self, exprs: &[P<ast::Expr>], attrs: &[Attribute]) {
1767         self.popen();
1768         self.print_inner_attributes_inline(attrs);
1769         self.commasep_exprs(Inconsistent, &exprs[..]);
1770         if exprs.len() == 1 {
1771             self.s.word(",");
1772         }
1773         self.pclose()
1774     }
1775
1776     fn print_expr_call(&mut self, func: &ast::Expr, args: &[P<ast::Expr>]) {
1777         let prec = match func.kind {
1778             ast::ExprKind::Field(..) => parser::PREC_FORCE_PAREN,
1779             _ => parser::PREC_POSTFIX,
1780         };
1781
1782         self.print_expr_maybe_paren(func, prec);
1783         self.print_call_post(args)
1784     }
1785
1786     fn print_expr_method_call(&mut self, segment: &ast::PathSegment, args: &[P<ast::Expr>]) {
1787         let base_args = &args[1..];
1788         self.print_expr_maybe_paren(&args[0], parser::PREC_POSTFIX);
1789         self.s.word(".");
1790         self.print_ident(segment.ident);
1791         if let Some(ref args) = segment.args {
1792             self.print_generic_args(args, true);
1793         }
1794         self.print_call_post(base_args)
1795     }
1796
1797     fn print_expr_binary(&mut self, op: ast::BinOp, lhs: &ast::Expr, rhs: &ast::Expr) {
1798         let assoc_op = AssocOp::from_ast_binop(op.node);
1799         let prec = assoc_op.precedence() as i8;
1800         let fixity = assoc_op.fixity();
1801
1802         let (left_prec, right_prec) = match fixity {
1803             Fixity::Left => (prec, prec + 1),
1804             Fixity::Right => (prec + 1, prec),
1805             Fixity::None => (prec + 1, prec + 1),
1806         };
1807
1808         let left_prec = match (&lhs.kind, op.node) {
1809             // These cases need parens: `x as i32 < y` has the parser thinking that `i32 < y` is
1810             // the beginning of a path type. It starts trying to parse `x as (i32 < y ...` instead
1811             // of `(x as i32) < ...`. We need to convince it _not_ to do that.
1812             (&ast::ExprKind::Cast { .. }, ast::BinOpKind::Lt)
1813             | (&ast::ExprKind::Cast { .. }, ast::BinOpKind::Shl) => parser::PREC_FORCE_PAREN,
1814             // We are given `(let _ = a) OP b`.
1815             //
1816             // - When `OP <= LAnd` we should print `let _ = a OP b` to avoid redundant parens
1817             //   as the parser will interpret this as `(let _ = a) OP b`.
1818             //
1819             // - Otherwise, e.g. when we have `(let a = b) < c` in AST,
1820             //   parens are required since the parser would interpret `let a = b < c` as
1821             //   `let a = (b < c)`. To achieve this, we force parens.
1822             (&ast::ExprKind::Let { .. }, _) if !parser::needs_par_as_let_scrutinee(prec) => {
1823                 parser::PREC_FORCE_PAREN
1824             }
1825             _ => left_prec,
1826         };
1827
1828         self.print_expr_maybe_paren(lhs, left_prec);
1829         self.s.space();
1830         self.word_space(op.node.to_string());
1831         self.print_expr_maybe_paren(rhs, right_prec)
1832     }
1833
1834     fn print_expr_unary(&mut self, op: ast::UnOp, expr: &ast::Expr) {
1835         self.s.word(ast::UnOp::to_string(op));
1836         self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
1837     }
1838
1839     fn print_expr_addr_of(
1840         &mut self,
1841         kind: ast::BorrowKind,
1842         mutability: ast::Mutability,
1843         expr: &ast::Expr,
1844     ) {
1845         self.s.word("&");
1846         match kind {
1847             ast::BorrowKind::Ref => self.print_mutability(mutability, false),
1848             ast::BorrowKind::Raw => {
1849                 self.word_nbsp("raw");
1850                 self.print_mutability(mutability, true);
1851             }
1852         }
1853         self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
1854     }
1855
1856     pub fn print_expr(&mut self, expr: &ast::Expr) {
1857         self.print_expr_outer_attr_style(expr, true)
1858     }
1859
1860     fn print_expr_outer_attr_style(&mut self, expr: &ast::Expr, is_inline: bool) {
1861         self.maybe_print_comment(expr.span.lo());
1862
1863         let attrs = &expr.attrs;
1864         if is_inline {
1865             self.print_outer_attributes_inline(attrs);
1866         } else {
1867             self.print_outer_attributes(attrs);
1868         }
1869
1870         self.ibox(INDENT_UNIT);
1871         self.ann.pre(self, AnnNode::Expr(expr));
1872         match expr.kind {
1873             ast::ExprKind::Box(ref expr) => {
1874                 self.word_space("box");
1875                 self.print_expr_maybe_paren(expr, parser::PREC_PREFIX);
1876             }
1877             ast::ExprKind::Array(ref exprs) => {
1878                 self.print_expr_vec(&exprs[..], attrs);
1879             }
1880             ast::ExprKind::Repeat(ref element, ref count) => {
1881                 self.print_expr_repeat(element, count, attrs);
1882             }
1883             ast::ExprKind::Struct(ref path, ref fields, ref wth) => {
1884                 self.print_expr_struct(path, &fields[..], wth, attrs);
1885             }
1886             ast::ExprKind::Tup(ref exprs) => {
1887                 self.print_expr_tup(&exprs[..], attrs);
1888             }
1889             ast::ExprKind::Call(ref func, ref args) => {
1890                 self.print_expr_call(func, &args[..]);
1891             }
1892             ast::ExprKind::MethodCall(ref segment, ref args) => {
1893                 self.print_expr_method_call(segment, &args[..]);
1894             }
1895             ast::ExprKind::Binary(op, ref lhs, ref rhs) => {
1896                 self.print_expr_binary(op, lhs, rhs);
1897             }
1898             ast::ExprKind::Unary(op, ref expr) => {
1899                 self.print_expr_unary(op, expr);
1900             }
1901             ast::ExprKind::AddrOf(k, m, ref expr) => {
1902                 self.print_expr_addr_of(k, m, expr);
1903             }
1904             ast::ExprKind::Lit(ref lit) => {
1905                 self.print_literal(lit);
1906             }
1907             ast::ExprKind::Cast(ref expr, ref ty) => {
1908                 let prec = AssocOp::As.precedence() as i8;
1909                 self.print_expr_maybe_paren(expr, prec);
1910                 self.s.space();
1911                 self.word_space("as");
1912                 self.print_type(ty);
1913             }
1914             ast::ExprKind::Type(ref expr, ref ty) => {
1915                 let prec = AssocOp::Colon.precedence() as i8;
1916                 self.print_expr_maybe_paren(expr, prec);
1917                 self.word_space(":");
1918                 self.print_type(ty);
1919             }
1920             ast::ExprKind::Let(ref pat, ref scrutinee) => {
1921                 self.print_let(pat, scrutinee);
1922             }
1923             ast::ExprKind::If(ref test, ref blk, ref elseopt) => {
1924                 self.print_if(test, blk, elseopt.as_deref())
1925             }
1926             ast::ExprKind::While(ref test, ref blk, opt_label) => {
1927                 if let Some(label) = opt_label {
1928                     self.print_ident(label.ident);
1929                     self.word_space(":");
1930                 }
1931                 self.head("while");
1932                 self.print_expr_as_cond(test);
1933                 self.s.space();
1934                 self.print_block_with_attrs(blk, attrs);
1935             }
1936             ast::ExprKind::ForLoop(ref pat, ref iter, ref blk, opt_label) => {
1937                 if let Some(label) = opt_label {
1938                     self.print_ident(label.ident);
1939                     self.word_space(":");
1940                 }
1941                 self.head("for");
1942                 self.print_pat(pat);
1943                 self.s.space();
1944                 self.word_space("in");
1945                 self.print_expr_as_cond(iter);
1946                 self.s.space();
1947                 self.print_block_with_attrs(blk, attrs);
1948             }
1949             ast::ExprKind::Loop(ref blk, opt_label) => {
1950                 if let Some(label) = opt_label {
1951                     self.print_ident(label.ident);
1952                     self.word_space(":");
1953                 }
1954                 self.head("loop");
1955                 self.s.space();
1956                 self.print_block_with_attrs(blk, attrs);
1957             }
1958             ast::ExprKind::Match(ref expr, ref arms) => {
1959                 self.cbox(INDENT_UNIT);
1960                 self.ibox(INDENT_UNIT);
1961                 self.word_nbsp("match");
1962                 self.print_expr_as_cond(expr);
1963                 self.s.space();
1964                 self.bopen();
1965                 self.print_inner_attributes_no_trailing_hardbreak(attrs);
1966                 for arm in arms {
1967                     self.print_arm(arm);
1968                 }
1969                 self.bclose(expr.span);
1970             }
1971             ast::ExprKind::Closure(
1972                 capture_clause,
1973                 asyncness,
1974                 movability,
1975                 ref decl,
1976                 ref body,
1977                 _,
1978             ) => {
1979                 self.print_movability(movability);
1980                 self.print_asyncness(asyncness);
1981                 self.print_capture_clause(capture_clause);
1982
1983                 self.print_fn_params_and_ret(decl, true);
1984                 self.s.space();
1985                 self.print_expr(body);
1986                 self.end(); // need to close a box
1987
1988                 // a box will be closed by print_expr, but we didn't want an overall
1989                 // wrapper so we closed the corresponding opening. so create an
1990                 // empty box to satisfy the close.
1991                 self.ibox(0);
1992             }
1993             ast::ExprKind::Block(ref blk, opt_label) => {
1994                 if let Some(label) = opt_label {
1995                     self.print_ident(label.ident);
1996                     self.word_space(":");
1997                 }
1998                 // containing cbox, will be closed by print-block at }
1999                 self.cbox(INDENT_UNIT);
2000                 // head-box, will be closed by print-block after {
2001                 self.ibox(0);
2002                 self.print_block_with_attrs(blk, attrs);
2003             }
2004             ast::ExprKind::Async(capture_clause, _, ref blk) => {
2005                 self.word_nbsp("async");
2006                 self.print_capture_clause(capture_clause);
2007                 self.s.space();
2008                 // cbox/ibox in analogy to the `ExprKind::Block` arm above
2009                 self.cbox(INDENT_UNIT);
2010                 self.ibox(0);
2011                 self.print_block_with_attrs(blk, attrs);
2012             }
2013             ast::ExprKind::Await(ref expr) => {
2014                 self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX);
2015                 self.s.word(".await");
2016             }
2017             ast::ExprKind::Assign(ref lhs, ref rhs, _) => {
2018                 let prec = AssocOp::Assign.precedence() as i8;
2019                 self.print_expr_maybe_paren(lhs, prec + 1);
2020                 self.s.space();
2021                 self.word_space("=");
2022                 self.print_expr_maybe_paren(rhs, prec);
2023             }
2024             ast::ExprKind::AssignOp(op, ref lhs, ref rhs) => {
2025                 let prec = AssocOp::Assign.precedence() as i8;
2026                 self.print_expr_maybe_paren(lhs, prec + 1);
2027                 self.s.space();
2028                 self.s.word(op.node.to_string());
2029                 self.word_space("=");
2030                 self.print_expr_maybe_paren(rhs, prec);
2031             }
2032             ast::ExprKind::Field(ref expr, ident) => {
2033                 self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX);
2034                 self.s.word(".");
2035                 self.print_ident(ident);
2036             }
2037             ast::ExprKind::Index(ref expr, ref index) => {
2038                 self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX);
2039                 self.s.word("[");
2040                 self.print_expr(index);
2041                 self.s.word("]");
2042             }
2043             ast::ExprKind::Range(ref start, ref end, limits) => {
2044                 // Special case for `Range`.  `AssocOp` claims that `Range` has higher precedence
2045                 // than `Assign`, but `x .. x = x` gives a parse error instead of `x .. (x = x)`.
2046                 // Here we use a fake precedence value so that any child with lower precedence than
2047                 // a "normal" binop gets parenthesized.  (`LOr` is the lowest-precedence binop.)
2048                 let fake_prec = AssocOp::LOr.precedence() as i8;
2049                 if let Some(ref e) = *start {
2050                     self.print_expr_maybe_paren(e, fake_prec);
2051                 }
2052                 if limits == ast::RangeLimits::HalfOpen {
2053                     self.s.word("..");
2054                 } else {
2055                     self.s.word("..=");
2056                 }
2057                 if let Some(ref e) = *end {
2058                     self.print_expr_maybe_paren(e, fake_prec);
2059                 }
2060             }
2061             ast::ExprKind::Path(None, ref path) => self.print_path(path, true, 0),
2062             ast::ExprKind::Path(Some(ref qself), ref path) => self.print_qpath(path, qself, true),
2063             ast::ExprKind::Break(opt_label, ref opt_expr) => {
2064                 self.s.word("break");
2065                 self.s.space();
2066                 if let Some(label) = opt_label {
2067                     self.print_ident(label.ident);
2068                     self.s.space();
2069                 }
2070                 if let Some(ref expr) = *opt_expr {
2071                     self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
2072                     self.s.space();
2073                 }
2074             }
2075             ast::ExprKind::Continue(opt_label) => {
2076                 self.s.word("continue");
2077                 self.s.space();
2078                 if let Some(label) = opt_label {
2079                     self.print_ident(label.ident);
2080                     self.s.space()
2081                 }
2082             }
2083             ast::ExprKind::Ret(ref result) => {
2084                 self.s.word("return");
2085                 if let Some(ref expr) = *result {
2086                     self.s.word(" ");
2087                     self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
2088                 }
2089             }
2090             ast::ExprKind::InlineAsm(ref a) => {
2091                 self.s.word("asm!");
2092                 self.popen();
2093                 self.print_string(&a.asm.as_str(), a.asm_str_style);
2094                 self.word_space(":");
2095
2096                 self.commasep(Inconsistent, &a.outputs, |s, out| {
2097                     let constraint = out.constraint.as_str();
2098                     let mut ch = constraint.chars();
2099                     match ch.next() {
2100                         Some('=') if out.is_rw => {
2101                             s.print_string(&format!("+{}", ch.as_str()), ast::StrStyle::Cooked)
2102                         }
2103                         _ => s.print_string(&constraint, ast::StrStyle::Cooked),
2104                     }
2105                     s.popen();
2106                     s.print_expr(&out.expr);
2107                     s.pclose();
2108                 });
2109                 self.s.space();
2110                 self.word_space(":");
2111
2112                 self.commasep(Inconsistent, &a.inputs, |s, &(co, ref o)| {
2113                     s.print_string(&co.as_str(), ast::StrStyle::Cooked);
2114                     s.popen();
2115                     s.print_expr(o);
2116                     s.pclose();
2117                 });
2118                 self.s.space();
2119                 self.word_space(":");
2120
2121                 self.commasep(Inconsistent, &a.clobbers, |s, co| {
2122                     s.print_string(&co.as_str(), ast::StrStyle::Cooked);
2123                 });
2124
2125                 let mut options = vec![];
2126                 if a.volatile {
2127                     options.push("volatile");
2128                 }
2129                 if a.alignstack {
2130                     options.push("alignstack");
2131                 }
2132                 if a.dialect == ast::AsmDialect::Intel {
2133                     options.push("intel");
2134                 }
2135
2136                 if !options.is_empty() {
2137                     self.s.space();
2138                     self.word_space(":");
2139                     self.commasep(Inconsistent, &options, |s, &co| {
2140                         s.print_string(co, ast::StrStyle::Cooked);
2141                     });
2142                 }
2143
2144                 self.pclose();
2145             }
2146             ast::ExprKind::Mac(ref m) => self.print_mac(m),
2147             ast::ExprKind::Paren(ref e) => {
2148                 self.popen();
2149                 self.print_inner_attributes_inline(attrs);
2150                 self.print_expr(e);
2151                 self.pclose();
2152             }
2153             ast::ExprKind::Yield(ref e) => {
2154                 self.s.word("yield");
2155                 match *e {
2156                     Some(ref expr) => {
2157                         self.s.space();
2158                         self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
2159                     }
2160                     _ => (),
2161                 }
2162             }
2163             ast::ExprKind::Try(ref e) => {
2164                 self.print_expr_maybe_paren(e, parser::PREC_POSTFIX);
2165                 self.s.word("?")
2166             }
2167             ast::ExprKind::TryBlock(ref blk) => {
2168                 self.head("try");
2169                 self.s.space();
2170                 self.print_block_with_attrs(blk, attrs)
2171             }
2172             ast::ExprKind::Err => {
2173                 self.popen();
2174                 self.s.word("/*ERROR*/");
2175                 self.pclose()
2176             }
2177         }
2178         self.ann.post(self, AnnNode::Expr(expr));
2179         self.end();
2180     }
2181
2182     crate fn print_local_decl(&mut self, loc: &ast::Local) {
2183         self.print_pat(&loc.pat);
2184         if let Some(ref ty) = loc.ty {
2185             self.word_space(":");
2186             self.print_type(ty);
2187         }
2188     }
2189
2190     pub fn print_usize(&mut self, i: usize) {
2191         self.s.word(i.to_string())
2192     }
2193
2194     crate fn print_name(&mut self, name: ast::Name) {
2195         self.s.word(name.to_string());
2196         self.ann.post(self, AnnNode::Name(&name))
2197     }
2198
2199     fn print_qpath(&mut self, path: &ast::Path, qself: &ast::QSelf, colons_before_params: bool) {
2200         self.s.word("<");
2201         self.print_type(&qself.ty);
2202         if qself.position > 0 {
2203             self.s.space();
2204             self.word_space("as");
2205             let depth = path.segments.len() - qself.position;
2206             self.print_path(path, false, depth);
2207         }
2208         self.s.word(">");
2209         self.s.word("::");
2210         let item_segment = path.segments.last().unwrap();
2211         self.print_ident(item_segment.ident);
2212         match item_segment.args {
2213             Some(ref args) => self.print_generic_args(args, colons_before_params),
2214             None => {}
2215         }
2216     }
2217
2218     crate fn print_pat(&mut self, pat: &ast::Pat) {
2219         self.maybe_print_comment(pat.span.lo());
2220         self.ann.pre(self, AnnNode::Pat(pat));
2221         /* Pat isn't normalized, but the beauty of it
2222         is that it doesn't matter */
2223         match pat.kind {
2224             PatKind::Wild => self.s.word("_"),
2225             PatKind::Ident(binding_mode, ident, ref sub) => {
2226                 match binding_mode {
2227                     ast::BindingMode::ByRef(mutbl) => {
2228                         self.word_nbsp("ref");
2229                         self.print_mutability(mutbl, false);
2230                     }
2231                     ast::BindingMode::ByValue(ast::Mutability::Not) => {}
2232                     ast::BindingMode::ByValue(ast::Mutability::Mut) => {
2233                         self.word_nbsp("mut");
2234                     }
2235                 }
2236                 self.print_ident(ident);
2237                 if let Some(ref p) = *sub {
2238                     self.s.space();
2239                     self.s.word_space("@");
2240                     self.print_pat(p);
2241                 }
2242             }
2243             PatKind::TupleStruct(ref path, ref elts) => {
2244                 self.print_path(path, true, 0);
2245                 self.popen();
2246                 self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(p));
2247                 self.pclose();
2248             }
2249             PatKind::Or(ref pats) => {
2250                 self.strsep("|", true, Inconsistent, &pats[..], |s, p| s.print_pat(p));
2251             }
2252             PatKind::Path(None, ref path) => {
2253                 self.print_path(path, true, 0);
2254             }
2255             PatKind::Path(Some(ref qself), ref path) => {
2256                 self.print_qpath(path, qself, false);
2257             }
2258             PatKind::Struct(ref path, ref fields, etc) => {
2259                 self.print_path(path, true, 0);
2260                 self.nbsp();
2261                 self.word_space("{");
2262                 self.commasep_cmnt(
2263                     Consistent,
2264                     &fields[..],
2265                     |s, f| {
2266                         s.cbox(INDENT_UNIT);
2267                         if !f.is_shorthand {
2268                             s.print_ident(f.ident);
2269                             s.word_nbsp(":");
2270                         }
2271                         s.print_pat(&f.pat);
2272                         s.end();
2273                     },
2274                     |f| f.pat.span,
2275                 );
2276                 if etc {
2277                     if !fields.is_empty() {
2278                         self.word_space(",");
2279                     }
2280                     self.s.word("..");
2281                 }
2282                 self.s.space();
2283                 self.s.word("}");
2284             }
2285             PatKind::Tuple(ref elts) => {
2286                 self.popen();
2287                 self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(p));
2288                 if elts.len() == 1 {
2289                     self.s.word(",");
2290                 }
2291                 self.pclose();
2292             }
2293             PatKind::Box(ref inner) => {
2294                 self.s.word("box ");
2295                 self.print_pat(inner);
2296             }
2297             PatKind::Ref(ref inner, mutbl) => {
2298                 self.s.word("&");
2299                 if mutbl == ast::Mutability::Mut {
2300                     self.s.word("mut ");
2301                 }
2302                 self.print_pat(inner);
2303             }
2304             PatKind::Lit(ref e) => self.print_expr(&**e),
2305             PatKind::Range(ref begin, ref end, Spanned { node: ref end_kind, .. }) => {
2306                 if let Some(e) = begin {
2307                     self.print_expr(e);
2308                     self.s.space();
2309                 }
2310                 match *end_kind {
2311                     RangeEnd::Included(RangeSyntax::DotDotDot) => self.s.word("..."),
2312                     RangeEnd::Included(RangeSyntax::DotDotEq) => self.s.word("..="),
2313                     RangeEnd::Excluded => self.s.word(".."),
2314                 }
2315                 if let Some(e) = end {
2316                     self.print_expr(e);
2317                 }
2318             }
2319             PatKind::Slice(ref elts) => {
2320                 self.s.word("[");
2321                 self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(p));
2322                 self.s.word("]");
2323             }
2324             PatKind::Rest => self.s.word(".."),
2325             PatKind::Paren(ref inner) => {
2326                 self.popen();
2327                 self.print_pat(inner);
2328                 self.pclose();
2329             }
2330             PatKind::Mac(ref m) => self.print_mac(m),
2331         }
2332         self.ann.post(self, AnnNode::Pat(pat))
2333     }
2334
2335     fn print_arm(&mut self, arm: &ast::Arm) {
2336         // Note, I have no idea why this check is necessary, but here it is.
2337         if arm.attrs.is_empty() {
2338             self.s.space();
2339         }
2340         self.cbox(INDENT_UNIT);
2341         self.ibox(0);
2342         self.maybe_print_comment(arm.pat.span.lo());
2343         self.print_outer_attributes(&arm.attrs);
2344         self.print_pat(&arm.pat);
2345         self.s.space();
2346         if let Some(ref e) = arm.guard {
2347             self.word_space("if");
2348             self.print_expr(e);
2349             self.s.space();
2350         }
2351         self.word_space("=>");
2352
2353         match arm.body.kind {
2354             ast::ExprKind::Block(ref blk, opt_label) => {
2355                 if let Some(label) = opt_label {
2356                     self.print_ident(label.ident);
2357                     self.word_space(":");
2358                 }
2359
2360                 // The block will close the pattern's ibox.
2361                 self.print_block_unclosed_indent(blk);
2362
2363                 // If it is a user-provided unsafe block, print a comma after it.
2364                 if let BlockCheckMode::Unsafe(ast::UserProvided) = blk.rules {
2365                     self.s.word(",");
2366                 }
2367             }
2368             _ => {
2369                 self.end(); // Close the ibox for the pattern.
2370                 self.print_expr(&arm.body);
2371                 self.s.word(",");
2372             }
2373         }
2374         self.end(); // Close enclosing cbox.
2375     }
2376
2377     fn print_explicit_self(&mut self, explicit_self: &ast::ExplicitSelf) {
2378         match explicit_self.node {
2379             SelfKind::Value(m) => {
2380                 self.print_mutability(m, false);
2381                 self.s.word("self")
2382             }
2383             SelfKind::Region(ref lt, m) => {
2384                 self.s.word("&");
2385                 self.print_opt_lifetime(lt);
2386                 self.print_mutability(m, false);
2387                 self.s.word("self")
2388             }
2389             SelfKind::Explicit(ref typ, m) => {
2390                 self.print_mutability(m, false);
2391                 self.s.word("self");
2392                 self.word_space(":");
2393                 self.print_type(typ)
2394             }
2395         }
2396     }
2397
2398     fn print_fn_full(
2399         &mut self,
2400         sig: &ast::FnSig,
2401         name: ast::Ident,
2402         generics: &ast::Generics,
2403         vis: &ast::Visibility,
2404         body: Option<&ast::Block>,
2405         attrs: &[ast::Attribute],
2406     ) {
2407         if body.is_some() {
2408             self.head("");
2409         }
2410         self.print_fn(&sig.decl, sig.header, Some(name), generics, vis);
2411         if let Some(body) = body {
2412             self.nbsp();
2413             self.print_block_with_attrs(body, attrs);
2414         } else {
2415             self.s.word(";");
2416         }
2417     }
2418
2419     crate fn print_fn(
2420         &mut self,
2421         decl: &ast::FnDecl,
2422         header: ast::FnHeader,
2423         name: Option<ast::Ident>,
2424         generics: &ast::Generics,
2425         vis: &ast::Visibility,
2426     ) {
2427         self.print_fn_header_info(header, vis);
2428
2429         if let Some(name) = name {
2430             self.nbsp();
2431             self.print_ident(name);
2432         }
2433         self.print_generic_params(&generics.params);
2434         self.print_fn_params_and_ret(decl, false);
2435         self.print_where_clause(&generics.where_clause)
2436     }
2437
2438     crate fn print_fn_params_and_ret(&mut self, decl: &ast::FnDecl, is_closure: bool) {
2439         let (open, close) = if is_closure { ("|", "|") } else { ("(", ")") };
2440         self.word(open);
2441         self.commasep(Inconsistent, &decl.inputs, |s, param| s.print_param(param, is_closure));
2442         self.word(close);
2443         self.print_fn_ret_ty(&decl.output)
2444     }
2445
2446     crate fn print_movability(&mut self, movability: ast::Movability) {
2447         match movability {
2448             ast::Movability::Static => self.word_space("static"),
2449             ast::Movability::Movable => {}
2450         }
2451     }
2452
2453     crate fn print_asyncness(&mut self, asyncness: ast::Async) {
2454         if asyncness.is_async() {
2455             self.word_nbsp("async");
2456         }
2457     }
2458
2459     crate fn print_capture_clause(&mut self, capture_clause: ast::CaptureBy) {
2460         match capture_clause {
2461             ast::CaptureBy::Value => self.word_space("move"),
2462             ast::CaptureBy::Ref => {}
2463         }
2464     }
2465
2466     pub fn print_type_bounds(&mut self, prefix: &'static str, bounds: &[ast::GenericBound]) {
2467         if !bounds.is_empty() {
2468             self.s.word(prefix);
2469             let mut first = true;
2470             for bound in bounds {
2471                 if !(first && prefix.is_empty()) {
2472                     self.nbsp();
2473                 }
2474                 if first {
2475                     first = false;
2476                 } else {
2477                     self.word_space("+");
2478                 }
2479
2480                 match bound {
2481                     GenericBound::Trait(tref, modifier) => {
2482                         if modifier == &TraitBoundModifier::Maybe {
2483                             self.s.word("?");
2484                         }
2485                         self.print_poly_trait_ref(tref);
2486                     }
2487                     GenericBound::Outlives(lt) => self.print_lifetime(*lt),
2488                 }
2489             }
2490         }
2491     }
2492
2493     crate fn print_lifetime(&mut self, lifetime: ast::Lifetime) {
2494         self.print_name(lifetime.ident.name)
2495     }
2496
2497     crate fn print_lifetime_bounds(
2498         &mut self,
2499         lifetime: ast::Lifetime,
2500         bounds: &ast::GenericBounds,
2501     ) {
2502         self.print_lifetime(lifetime);
2503         if !bounds.is_empty() {
2504             self.s.word(": ");
2505             for (i, bound) in bounds.iter().enumerate() {
2506                 if i != 0 {
2507                     self.s.word(" + ");
2508                 }
2509                 match bound {
2510                     ast::GenericBound::Outlives(lt) => self.print_lifetime(*lt),
2511                     _ => panic!(),
2512                 }
2513             }
2514         }
2515     }
2516
2517     crate fn print_generic_params(&mut self, generic_params: &[ast::GenericParam]) {
2518         if generic_params.is_empty() {
2519             return;
2520         }
2521
2522         self.s.word("<");
2523
2524         self.commasep(Inconsistent, &generic_params, |s, param| {
2525             s.print_outer_attributes_inline(&param.attrs);
2526
2527             match param.kind {
2528                 ast::GenericParamKind::Lifetime => {
2529                     let lt = ast::Lifetime { id: param.id, ident: param.ident };
2530                     s.print_lifetime_bounds(lt, &param.bounds)
2531                 }
2532                 ast::GenericParamKind::Type { ref default } => {
2533                     s.print_ident(param.ident);
2534                     s.print_type_bounds(":", &param.bounds);
2535                     if let Some(ref default) = default {
2536                         s.s.space();
2537                         s.word_space("=");
2538                         s.print_type(default)
2539                     }
2540                 }
2541                 ast::GenericParamKind::Const { ref ty } => {
2542                     s.word_space("const");
2543                     s.print_ident(param.ident);
2544                     s.s.space();
2545                     s.word_space(":");
2546                     s.print_type(ty);
2547                     s.print_type_bounds(":", &param.bounds)
2548                 }
2549             }
2550         });
2551
2552         self.s.word(">");
2553     }
2554
2555     crate fn print_where_clause(&mut self, where_clause: &ast::WhereClause) {
2556         if where_clause.predicates.is_empty() {
2557             return;
2558         }
2559
2560         self.s.space();
2561         self.word_space("where");
2562
2563         for (i, predicate) in where_clause.predicates.iter().enumerate() {
2564             if i != 0 {
2565                 self.word_space(",");
2566             }
2567
2568             match *predicate {
2569                 ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
2570                     ref bound_generic_params,
2571                     ref bounded_ty,
2572                     ref bounds,
2573                     ..
2574                 }) => {
2575                     self.print_formal_generic_params(bound_generic_params);
2576                     self.print_type(bounded_ty);
2577                     self.print_type_bounds(":", bounds);
2578                 }
2579                 ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
2580                     ref lifetime,
2581                     ref bounds,
2582                     ..
2583                 }) => {
2584                     self.print_lifetime_bounds(*lifetime, bounds);
2585                 }
2586                 ast::WherePredicate::EqPredicate(ast::WhereEqPredicate {
2587                     ref lhs_ty,
2588                     ref rhs_ty,
2589                     ..
2590                 }) => {
2591                     self.print_type(lhs_ty);
2592                     self.s.space();
2593                     self.word_space("=");
2594                     self.print_type(rhs_ty);
2595                 }
2596             }
2597         }
2598     }
2599
2600     crate fn print_use_tree(&mut self, tree: &ast::UseTree) {
2601         match tree.kind {
2602             ast::UseTreeKind::Simple(rename, ..) => {
2603                 self.print_path(&tree.prefix, false, 0);
2604                 if let Some(rename) = rename {
2605                     self.s.space();
2606                     self.word_space("as");
2607                     self.print_ident(rename);
2608                 }
2609             }
2610             ast::UseTreeKind::Glob => {
2611                 if !tree.prefix.segments.is_empty() {
2612                     self.print_path(&tree.prefix, false, 0);
2613                     self.s.word("::");
2614                 }
2615                 self.s.word("*");
2616             }
2617             ast::UseTreeKind::Nested(ref items) => {
2618                 if tree.prefix.segments.is_empty() {
2619                     self.s.word("{");
2620                 } else {
2621                     self.print_path(&tree.prefix, false, 0);
2622                     self.s.word("::{");
2623                 }
2624                 self.commasep(Inconsistent, &items[..], |this, &(ref tree, _)| {
2625                     this.print_use_tree(tree)
2626                 });
2627                 self.s.word("}");
2628             }
2629         }
2630     }
2631
2632     pub fn print_mutability(&mut self, mutbl: ast::Mutability, print_const: bool) {
2633         match mutbl {
2634             ast::Mutability::Mut => self.word_nbsp("mut"),
2635             ast::Mutability::Not => {
2636                 if print_const {
2637                     self.word_nbsp("const");
2638                 }
2639             }
2640         }
2641     }
2642
2643     crate fn print_mt(&mut self, mt: &ast::MutTy, print_const: bool) {
2644         self.print_mutability(mt.mutbl, print_const);
2645         self.print_type(&mt.ty)
2646     }
2647
2648     crate fn print_param(&mut self, input: &ast::Param, is_closure: bool) {
2649         self.ibox(INDENT_UNIT);
2650
2651         self.print_outer_attributes_inline(&input.attrs);
2652
2653         match input.ty.kind {
2654             ast::TyKind::Infer if is_closure => self.print_pat(&input.pat),
2655             _ => {
2656                 if let Some(eself) = input.to_self() {
2657                     self.print_explicit_self(&eself);
2658                 } else {
2659                     let invalid = if let PatKind::Ident(_, ident, _) = input.pat.kind {
2660                         ident.name == kw::Invalid
2661                     } else {
2662                         false
2663                     };
2664                     if !invalid {
2665                         self.print_pat(&input.pat);
2666                         self.s.word(":");
2667                         self.s.space();
2668                     }
2669                     self.print_type(&input.ty);
2670                 }
2671             }
2672         }
2673         self.end();
2674     }
2675
2676     crate fn print_fn_ret_ty(&mut self, fn_ret_ty: &ast::FunctionRetTy) {
2677         if let ast::FunctionRetTy::Ty(ty) = fn_ret_ty {
2678             self.space_if_not_bol();
2679             self.ibox(INDENT_UNIT);
2680             self.word_space("->");
2681             self.print_type(ty);
2682             self.end();
2683             self.maybe_print_comment(ty.span.lo());
2684         }
2685     }
2686
2687     crate fn print_ty_fn(
2688         &mut self,
2689         ext: ast::Extern,
2690         unsafety: ast::Unsafe,
2691         decl: &ast::FnDecl,
2692         name: Option<ast::Ident>,
2693         generic_params: &[ast::GenericParam],
2694     ) {
2695         self.ibox(INDENT_UNIT);
2696         if !generic_params.is_empty() {
2697             self.s.word("for");
2698             self.print_generic_params(generic_params);
2699         }
2700         let generics = ast::Generics {
2701             params: Vec::new(),
2702             where_clause: ast::WhereClause { predicates: Vec::new(), span: rustc_span::DUMMY_SP },
2703             span: rustc_span::DUMMY_SP,
2704         };
2705         let header = ast::FnHeader { unsafety, ext, ..ast::FnHeader::default() };
2706         let vis = dummy_spanned(ast::VisibilityKind::Inherited);
2707         self.print_fn(decl, header, name, &generics, &vis);
2708         self.end();
2709     }
2710
2711     crate fn maybe_print_trailing_comment(
2712         &mut self,
2713         span: rustc_span::Span,
2714         next_pos: Option<BytePos>,
2715     ) {
2716         if let Some(cmnts) = self.comments() {
2717             if let Some(cmnt) = cmnts.trailing_comment(span, next_pos) {
2718                 self.print_comment(&cmnt);
2719             }
2720         }
2721     }
2722
2723     crate fn print_remaining_comments(&mut self) {
2724         // If there aren't any remaining comments, then we need to manually
2725         // make sure there is a line break at the end.
2726         if self.next_comment().is_none() {
2727             self.s.hardbreak();
2728         }
2729         while let Some(ref cmnt) = self.next_comment() {
2730             self.print_comment(cmnt);
2731         }
2732     }
2733
2734     crate fn print_fn_header_info(&mut self, header: ast::FnHeader, vis: &ast::Visibility) {
2735         self.s.word(visibility_qualified(vis, ""));
2736
2737         self.print_constness(header.constness);
2738         self.print_asyncness(header.asyncness);
2739         self.print_unsafety(header.unsafety);
2740
2741         match header.ext {
2742             ast::Extern::None => {}
2743             ast::Extern::Implicit => {
2744                 self.word_nbsp("extern");
2745             }
2746             ast::Extern::Explicit(abi) => {
2747                 self.word_nbsp("extern");
2748                 self.print_literal(&abi.as_lit());
2749                 self.nbsp();
2750             }
2751         }
2752
2753         self.s.word("fn")
2754     }
2755
2756     crate fn print_unsafety(&mut self, s: ast::Unsafe) {
2757         match s {
2758             ast::Unsafe::No => {}
2759             ast::Unsafe::Yes(_) => self.word_nbsp("unsafe"),
2760         }
2761     }
2762
2763     crate fn print_constness(&mut self, s: ast::Const) {
2764         match s {
2765             ast::Const::No => {}
2766             ast::Const::Yes(_) => self.word_nbsp("const"),
2767         }
2768     }
2769
2770     crate fn print_is_auto(&mut self, s: ast::IsAuto) {
2771         match s {
2772             ast::IsAuto::Yes => self.word_nbsp("auto"),
2773             ast::IsAuto::No => {}
2774         }
2775     }
2776 }