compiler/rustc_hir_pretty/src/lib.rs

   1 #![recursion_limit = "256"]
   2
   3 use rustc_ast as ast;
   4 use rustc_ast::util::parser::{self, AssocOp, Fixity};
   5 use rustc_ast_pretty::pp::Breaks::{Consistent, Inconsistent};
   6 use rustc_ast_pretty::pp::{self, Breaks};
   7 use rustc_ast_pretty::pprust::{Comments, PrintState};
   8 use rustc_hir as hir;
   9 use rustc_hir::{GenericArg, GenericParam, GenericParamKind, Node};
  10 use rustc_hir::{GenericBound, PatKind, RangeEnd, TraitBoundModifier};
  11 use rustc_span::source_map::{SourceMap, Spanned};
  12 use rustc_span::symbol::{kw, Ident, IdentPrinter, Symbol};
  13 use rustc_span::{self, BytePos, FileName};
  14 use rustc_target::spec::abi::Abi;
  15
  16 use std::borrow::Cow;
  17 use std::cell::Cell;
  18 use std::collections::BTreeMap;
  19 use std::vec;
  20
  21 pub fn id_to_string(map: &dyn rustc_hir::intravisit::Map<'_>, hir_id: hir::HirId) -> String {
  22     to_string(&map, |s| s.print_node(map.find(hir_id).unwrap()))
  23 }
  24
  25 pub enum AnnNode<'a> {
  26     Name(&'a Symbol),
  27     Block(&'a hir::Block<'a>),
  28     Item(&'a hir::Item<'a>),
  29     SubItem(hir::HirId),
  30     Expr(&'a hir::Expr<'a>),
  31     Pat(&'a hir::Pat<'a>),
  32     Arm(&'a hir::Arm<'a>),
  33 }
  34
  35 pub enum Nested {
  36     Item(hir::ItemId),
  37     TraitItem(hir::TraitItemId),
  38     ImplItem(hir::ImplItemId),
  39     ForeignItem(hir::ForeignItemId),
  40     Body(hir::BodyId),
  41     BodyParamPat(hir::BodyId, usize),
  42 }
  43
  44 pub trait PpAnn {
  45     fn nested(&self, _state: &mut State<'_>, _nested: Nested) {}
  46     fn pre(&self, _state: &mut State<'_>, _node: AnnNode<'_>) {}
  47     fn post(&self, _state: &mut State<'_>, _node: AnnNode<'_>) {}
  48 }
  49
  50 pub struct NoAnn;
  51 impl PpAnn for NoAnn {}
  52 pub const NO_ANN: &dyn PpAnn = &NoAnn;
  53
  54 impl PpAnn for hir::Crate<'_> {
  55     fn nested(&self, state: &mut State<'_>, nested: Nested) {
  56         match nested {
  57             Nested::Item(id) => state.print_item(self.item(id)),
  58             Nested::TraitItem(id) => state.print_trait_item(self.trait_item(id)),
  59             Nested::ImplItem(id) => state.print_impl_item(self.impl_item(id)),
  60             Nested::ForeignItem(id) => state.print_foreign_item(self.foreign_item(id)),
  61             Nested::Body(id) => state.print_expr(&self.body(id).value),
  62             Nested::BodyParamPat(id, i) => state.print_pat(&self.body(id).params[i].pat),
  63         }
  64     }
  65 }
  66
  67 /// Identical to the `PpAnn` implementation for `hir::Crate`,
  68 /// except it avoids creating a dependency on the whole crate.
  69 impl PpAnn for &dyn rustc_hir::intravisit::Map<'_> {
  70     fn nested(&self, state: &mut State<'_>, nested: Nested) {
  71         match nested {
  72             Nested::Item(id) => state.print_item(self.item(id)),
  73             Nested::TraitItem(id) => state.print_trait_item(self.trait_item(id)),
  74             Nested::ImplItem(id) => state.print_impl_item(self.impl_item(id)),
  75             Nested::ForeignItem(id) => state.print_foreign_item(self.foreign_item(id)),
  76             Nested::Body(id) => state.print_expr(&self.body(id).value),
  77             Nested::BodyParamPat(id, i) => state.print_pat(&self.body(id).params[i].pat),
  78         }
  79     }
  80 }
  81
  82 pub struct State<'a> {
  83     pub s: pp::Printer,
  84     comments: Option<Comments<'a>>,
  85     attrs: &'a BTreeMap<hir::HirId, &'a [ast::Attribute]>,
  86     ann: &'a (dyn PpAnn + 'a),
  87 }
  88
  89 impl<'a> State<'a> {
  90     pub fn print_node(&mut self, node: Node<'_>) {
  91         match node {
  92             Node::Param(a) => self.print_param(&a),
  93             Node::Item(a) => self.print_item(&a),
  94             Node::ForeignItem(a) => self.print_foreign_item(&a),
  95             Node::TraitItem(a) => self.print_trait_item(a),
  96             Node::ImplItem(a) => self.print_impl_item(a),
  97             Node::Variant(a) => self.print_variant(&a),
  98             Node::AnonConst(a) => self.print_anon_const(&a),
  99             Node::Expr(a) => self.print_expr(&a),
 100             Node::Stmt(a) => self.print_stmt(&a),
 101             Node::PathSegment(a) => self.print_path_segment(&a),
 102             Node::Ty(a) => self.print_type(&a),
 103             Node::TraitRef(a) => self.print_trait_ref(&a),
 104             Node::Binding(a) | Node::Pat(a) => self.print_pat(&a),
 105             Node::Arm(a) => self.print_arm(&a),
 106             Node::Block(a) => {
 107                 // Containing cbox, will be closed by print-block at `}`.
 108                 self.cbox(INDENT_UNIT);
 109                 // Head-ibox, will be closed by print-block after `{`.
 110                 self.ibox(0);
 111                 self.print_block(&a)
 112             }
 113             Node::Lifetime(a) => self.print_lifetime(&a),
 114             Node::Visibility(a) => self.print_visibility(&a),
 115             Node::GenericParam(_) => panic!("cannot print Node::GenericParam"),
 116             Node::Field(_) => panic!("cannot print Node::Field"),
 117             // These cases do not carry enough information in the
 118             // `hir_map` to reconstruct their full structure for pretty
 119             // printing.
 120             Node::Ctor(..) => panic!("cannot print isolated Ctor"),
 121             Node::Local(a) => self.print_local_decl(&a),
 122             Node::MacroDef(_) => panic!("cannot print MacroDef"),
 123             Node::Crate(..) => panic!("cannot print Crate"),
 124         }
 125     }
 126 }
 127
 128 impl std::ops::Deref for State<'_> {
 129     type Target = pp::Printer;
 130     fn deref(&self) -> &Self::Target {
 131         &self.s
 132     }
 133 }
 134
 135 impl std::ops::DerefMut for State<'_> {
 136     fn deref_mut(&mut self) -> &mut Self::Target {
 137         &mut self.s
 138     }
 139 }
 140
 141 impl<'a> PrintState<'a> for State<'a> {
 142     fn comments(&mut self) -> &mut Option<Comments<'a>> {
 143         &mut self.comments
 144     }
 145
 146     fn print_ident(&mut self, ident: Ident) {
 147         self.s.word(IdentPrinter::for_ast_ident(ident, ident.is_raw_guess()).to_string());
 148         self.ann.post(self, AnnNode::Name(&ident.name))
 149     }
 150
 151     fn print_generic_args(&mut self, _: &ast::GenericArgs, _colons_before_params: bool) {
 152         panic!("AST generic args printed by HIR pretty-printer");
 153     }
 154 }
 155
 156 pub const INDENT_UNIT: usize = 4;
 157
 158 /// Requires you to pass an input filename and reader so that
 159 /// it can scan the input text for comments to copy forward.
 160 pub fn print_crate<'a>(
 161     sm: &'a SourceMap,
 162     krate: &hir::Crate<'_>,
 163     filename: FileName,
 164     input: String,
 165     ann: &'a dyn PpAnn,
 166 ) -> String {
 167     let mut s = State::new_from_input(sm, filename, input, &krate.attrs, ann);
 168
 169     // When printing the AST, we sometimes need to inject `#[no_std]` here.
 170     // Since you can't compile the HIR, it's not necessary.
 171
 172     s.print_mod(&krate.item, s.attrs(hir::CRATE_HIR_ID));
 173     s.print_remaining_comments();
 174     s.s.eof()
 175 }
 176
 177 impl<'a> State<'a> {
 178     pub fn new_from_input(
 179         sm: &'a SourceMap,
 180         filename: FileName,
 181         input: String,
 182         attrs: &'a BTreeMap<hir::HirId, &[ast::Attribute]>,
 183         ann: &'a dyn PpAnn,
 184     ) -> State<'a> {
 185         State {
 186             s: pp::mk_printer(),
 187             comments: Some(Comments::new(sm, filename, input)),
 188             attrs,
 189             ann,
 190         }
 191     }
 192
 193     fn attrs(&self, id: hir::HirId) -> &'a [ast::Attribute] {
 194         self.attrs.get(&id).map_or(&[], |la| *la)
 195     }
 196 }
 197
 198 pub fn to_string<F>(ann: &dyn PpAnn, f: F) -> String
 199 where
 200     F: FnOnce(&mut State<'_>),
 201 {
 202     let mut printer =
 203         State { s: pp::mk_printer(), comments: None, attrs: &BTreeMap::default(), ann };
 204     f(&mut printer);
 205     printer.s.eof()
 206 }
 207
 208 pub fn visibility_qualified<S: Into<Cow<'static, str>>>(vis: &hir::Visibility<'_>, w: S) -> String {
 209     to_string(NO_ANN, |s| {
 210         s.print_visibility(vis);
 211         s.s.word(w)
 212     })
 213 }
 214
 215 pub fn generic_params_to_string(generic_params: &[GenericParam<'_>]) -> String {
 216     to_string(NO_ANN, |s| s.print_generic_params(generic_params))
 217 }
 218
 219 pub fn bounds_to_string<'b>(bounds: impl IntoIterator<Item = &'b hir::GenericBound<'b>>) -> String {
 220     to_string(NO_ANN, |s| s.print_bounds("", bounds))
 221 }
 222
 223 pub fn ty_to_string(ty: &hir::Ty<'_>) -> String {
 224     to_string(NO_ANN, |s| s.print_type(ty))
 225 }
 226
 227 pub fn path_segment_to_string(segment: &hir::PathSegment<'_>) -> String {
 228     to_string(NO_ANN, |s| s.print_path_segment(segment))
 229 }
 230
 231 pub fn path_to_string(segment: &hir::Path<'_>) -> String {
 232     to_string(NO_ANN, |s| s.print_path(segment, false))
 233 }
 234
 235 pub fn fn_to_string(
 236     decl: &hir::FnDecl<'_>,
 237     header: hir::FnHeader,
 238     name: Option<Symbol>,
 239     generics: &hir::Generics<'_>,
 240     vis: &hir::Visibility<'_>,
 241     arg_names: &[Ident],
 242     body_id: Option<hir::BodyId>,
 243 ) -> String {
 244     to_string(NO_ANN, |s| s.print_fn(decl, header, name, generics, vis, arg_names, body_id))
 245 }
 246
 247 pub fn enum_def_to_string(
 248     enum_definition: &hir::EnumDef<'_>,
 249     generics: &hir::Generics<'_>,
 250     name: Symbol,
 251     span: rustc_span::Span,
 252     visibility: &hir::Visibility<'_>,
 253 ) -> String {
 254     to_string(NO_ANN, |s| s.print_enum_def(enum_definition, generics, name, span, visibility))
 255 }
 256
 257 impl<'a> State<'a> {
 258     pub fn cbox(&mut self, u: usize) {
 259         self.s.cbox(u);
 260     }
 261
 262     pub fn nbsp(&mut self) {
 263         self.s.word(" ")
 264     }
 265
 266     pub fn word_nbsp<S: Into<Cow<'static, str>>>(&mut self, w: S) {
 267         self.s.word(w);
 268         self.nbsp()
 269     }
 270
 271     pub fn head<S: Into<Cow<'static, str>>>(&mut self, w: S) {
 272         let w = w.into();
 273         // outer-box is consistent
 274         self.cbox(INDENT_UNIT);
 275         // head-box is inconsistent
 276         self.ibox(w.len() + 1);
 277         // keyword that starts the head
 278         if !w.is_empty() {
 279             self.word_nbsp(w);
 280         }
 281     }
 282
 283     pub fn bopen(&mut self) {
 284         self.s.word("{");
 285         self.end(); // close the head-box
 286     }
 287
 288     pub fn bclose_maybe_open(&mut self, span: rustc_span::Span, close_box: bool) {
 289         self.maybe_print_comment(span.hi());
 290         self.break_offset_if_not_bol(1, -(INDENT_UNIT as isize));
 291         self.s.word("}");
 292         if close_box {
 293             self.end(); // close the outer-box
 294         }
 295     }
 296
 297     pub fn bclose(&mut self, span: rustc_span::Span) {
 298         self.bclose_maybe_open(span, true)
 299     }
 300
 301     pub fn space_if_not_bol(&mut self) {
 302         if !self.s.is_beginning_of_line() {
 303             self.s.space();
 304         }
 305     }
 306
 307     pub fn break_offset_if_not_bol(&mut self, n: usize, off: isize) {
 308         if !self.s.is_beginning_of_line() {
 309             self.s.break_offset(n, off)
 310         } else if off != 0 && self.s.last_token().is_hardbreak_tok() {
 311             // We do something pretty sketchy here: tuck the nonzero
 312             // offset-adjustment we were going to deposit along with the
 313             // break into the previous hardbreak.
 314             self.s.replace_last_token(pp::Printer::hardbreak_tok_offset(off));
 315         }
 316     }
 317
 318     // Synthesizes a comment that was not textually present in the original source
 319     // file.
 320     pub fn synth_comment(&mut self, text: String) {
 321         self.s.word("/*");
 322         self.s.space();
 323         self.s.word(text);
 324         self.s.space();
 325         self.s.word("*/")
 326     }
 327
 328     pub fn commasep_cmnt<T, F, G>(&mut self, b: Breaks, elts: &[T], mut op: F, mut get_span: G)
 329     where
 330         F: FnMut(&mut State<'_>, &T),
 331         G: FnMut(&T) -> rustc_span::Span,
 332     {
 333         self.rbox(0, b);
 334         let len = elts.len();
 335         let mut i = 0;
 336         for elt in elts {
 337             self.maybe_print_comment(get_span(elt).hi());
 338             op(self, elt);
 339             i += 1;
 340             if i < len {
 341                 self.s.word(",");
 342                 self.maybe_print_trailing_comment(get_span(elt), Some(get_span(&elts[i]).hi()));
 343                 self.space_if_not_bol();
 344             }
 345         }
 346         self.end();
 347     }
 348
 349     pub fn commasep_exprs(&mut self, b: Breaks, exprs: &[hir::Expr<'_>]) {
 350         self.commasep_cmnt(b, exprs, |s, e| s.print_expr(&e), |e| e.span)
 351     }
 352
 353     pub fn print_mod(&mut self, _mod: &hir::Mod<'_>, attrs: &[ast::Attribute]) {
 354         self.print_inner_attributes(attrs);
 355         for &item_id in _mod.item_ids {
 356             self.ann.nested(self, Nested::Item(item_id));
 357         }
 358     }
 359
 360     pub fn print_opt_lifetime(&mut self, lifetime: &hir::Lifetime) {
 361         if !lifetime.is_elided() {
 362             self.print_lifetime(lifetime);
 363             self.nbsp();
 364         }
 365     }
 366
 367     pub fn print_type(&mut self, ty: &hir::Ty<'_>) {
 368         self.maybe_print_comment(ty.span.lo());
 369         self.ibox(0);
 370         match ty.kind {
 371             hir::TyKind::Slice(ref ty) => {
 372                 self.s.word("[");
 373                 self.print_type(&ty);
 374                 self.s.word("]");
 375             }
 376             hir::TyKind::Ptr(ref mt) => {
 377                 self.s.word("*");
 378                 self.print_mt(mt, true);
 379             }
 380             hir::TyKind::Rptr(ref lifetime, ref mt) => {
 381                 self.s.word("&");
 382                 self.print_opt_lifetime(lifetime);
 383                 self.print_mt(mt, false);
 384             }
 385             hir::TyKind::Never => {
 386                 self.s.word("!");
 387             }
 388             hir::TyKind::Tup(ref elts) => {
 389                 self.popen();
 390                 self.commasep(Inconsistent, &elts[..], |s, ty| s.print_type(&ty));
 391                 if elts.len() == 1 {
 392                     self.s.word(",");
 393                 }
 394                 self.pclose();
 395             }
 396             hir::TyKind::BareFn(ref f) => {
 397                 self.print_ty_fn(
 398                     f.abi,
 399                     f.unsafety,
 400                     &f.decl,
 401                     None,
 402                     &f.generic_params,
 403                     f.param_names,
 404                 );
 405             }
 406             hir::TyKind::OpaqueDef(..) => self.s.word("/*impl Trait*/"),
 407             hir::TyKind::Path(ref qpath) => self.print_qpath(qpath, false),
 408             hir::TyKind::TraitObject(bounds, ref lifetime, syntax) => {
 409                 if syntax == ast::TraitObjectSyntax::Dyn {
 410                     self.word_space("dyn");
 411                 }
 412                 let mut first = true;
 413                 for bound in bounds {
 414                     if first {
 415                         first = false;
 416                     } else {
 417                         self.nbsp();
 418                         self.word_space("+");
 419                     }
 420                     self.print_poly_trait_ref(bound);
 421                 }
 422                 if !lifetime.is_elided() {
 423                     self.nbsp();
 424                     self.word_space("+");
 425                     self.print_lifetime(lifetime);
 426                 }
 427             }
 428             hir::TyKind::Array(ref ty, ref length) => {
 429                 self.s.word("[");
 430                 self.print_type(&ty);
 431                 self.s.word("; ");
 432                 self.print_anon_const(length);
 433                 self.s.word("]");
 434             }
 435             hir::TyKind::Typeof(ref e) => {
 436                 self.s.word("typeof(");
 437                 self.print_anon_const(e);
 438                 self.s.word(")");
 439             }
 440             hir::TyKind::Infer => {
 441                 self.s.word("_");
 442             }
 443             hir::TyKind::Err => {
 444                 self.popen();
 445                 self.s.word("/*ERROR*/");
 446                 self.pclose();
 447             }
 448         }
 449         self.end()
 450     }
 451
 452     pub fn print_foreign_item(&mut self, item: &hir::ForeignItem<'_>) {
 453         self.hardbreak_if_not_bol();
 454         self.maybe_print_comment(item.span.lo());
 455         self.print_outer_attributes(self.attrs(item.hir_id()));
 456         match item.kind {
 457             hir::ForeignItemKind::Fn(ref decl, ref arg_names, ref generics) => {
 458                 self.head("");
 459                 self.print_fn(
 460                     decl,
 461                     hir::FnHeader {
 462                         unsafety: hir::Unsafety::Normal,
 463                         constness: hir::Constness::NotConst,
 464                         abi: Abi::Rust,
 465                         asyncness: hir::IsAsync::NotAsync,
 466                     },
 467                     Some(item.ident.name),
 468                     generics,
 469                     &item.vis,
 470                     arg_names,
 471                     None,
 472                 );
 473                 self.end(); // end head-ibox
 474                 self.s.word(";");
 475                 self.end() // end the outer fn box
 476             }
 477             hir::ForeignItemKind::Static(ref t, m) => {
 478                 self.head(visibility_qualified(&item.vis, "static"));
 479                 if m == hir::Mutability::Mut {
 480                     self.word_space("mut");
 481                 }
 482                 self.print_ident(item.ident);
 483                 self.word_space(":");
 484                 self.print_type(&t);
 485                 self.s.word(";");
 486                 self.end(); // end the head-ibox
 487                 self.end() // end the outer cbox
 488             }
 489             hir::ForeignItemKind::Type => {
 490                 self.head(visibility_qualified(&item.vis, "type"));
 491                 self.print_ident(item.ident);
 492                 self.s.word(";");
 493                 self.end(); // end the head-ibox
 494                 self.end() // end the outer cbox
 495             }
 496         }
 497     }
 498
 499     fn print_associated_const(
 500         &mut self,
 501         ident: Ident,
 502         ty: &hir::Ty<'_>,
 503         default: Option<hir::BodyId>,
 504         vis: &hir::Visibility<'_>,
 505     ) {
 506         self.s.word(visibility_qualified(vis, ""));
 507         self.word_space("const");
 508         self.print_ident(ident);
 509         self.word_space(":");
 510         self.print_type(ty);
 511         if let Some(expr) = default {
 512             self.s.space();
 513             self.word_space("=");
 514             self.ann.nested(self, Nested::Body(expr));
 515         }
 516         self.s.word(";")
 517     }
 518
 519     fn print_associated_type(
 520         &mut self,
 521         ident: Ident,
 522         generics: &hir::Generics<'_>,
 523         bounds: Option<hir::GenericBounds<'_>>,
 524         ty: Option<&hir::Ty<'_>>,
 525     ) {
 526         self.word_space("type");
 527         self.print_ident(ident);
 528         self.print_generic_params(&generics.params);
 529         if let Some(bounds) = bounds {
 530             self.print_bounds(":", bounds);
 531         }
 532         self.print_where_clause(&generics.where_clause);
 533         if let Some(ty) = ty {
 534             self.s.space();
 535             self.word_space("=");
 536             self.print_type(ty);
 537         }
 538         self.s.word(";")
 539     }
 540
 541     fn print_item_type(
 542         &mut self,
 543         item: &hir::Item<'_>,
 544         generics: &hir::Generics<'_>,
 545         inner: impl Fn(&mut Self),
 546     ) {
 547         self.head(visibility_qualified(&item.vis, "type"));
 548         self.print_ident(item.ident);
 549         self.print_generic_params(&generics.params);
 550         self.end(); // end the inner ibox
 551
 552         self.print_where_clause(&generics.where_clause);
 553         self.s.space();
 554         inner(self);
 555         self.s.word(";");
 556         self.end(); // end the outer ibox
 557     }
 558
 559     /// Pretty-print an item
 560     pub fn print_item(&mut self, item: &hir::Item<'_>) {
 561         self.hardbreak_if_not_bol();
 562         self.maybe_print_comment(item.span.lo());
 563         let attrs = self.attrs(item.hir_id());
 564         self.print_outer_attributes(attrs);
 565         self.ann.pre(self, AnnNode::Item(item));
 566         match item.kind {
 567             hir::ItemKind::ExternCrate(orig_name) => {
 568                 self.head(visibility_qualified(&item.vis, "extern crate"));
 569                 if let Some(orig_name) = orig_name {
 570                     self.print_name(orig_name);
 571                     self.s.space();
 572                     self.s.word("as");
 573                     self.s.space();
 574                 }
 575                 self.print_ident(item.ident);
 576                 self.s.word(";");
 577                 self.end(); // end inner head-block
 578                 self.end(); // end outer head-block
 579             }
 580             hir::ItemKind::Use(ref path, kind) => {
 581                 self.head(visibility_qualified(&item.vis, "use"));
 582                 self.print_path(path, false);
 583
 584                 match kind {
 585                     hir::UseKind::Single => {
 586                         if path.segments.last().unwrap().ident != item.ident {
 587                             self.s.space();
 588                             self.word_space("as");
 589                             self.print_ident(item.ident);
 590                         }
 591                         self.s.word(";");
 592                     }
 593                     hir::UseKind::Glob => self.s.word("::*;"),
 594                     hir::UseKind::ListStem => self.s.word("::{};"),
 595                 }
 596                 self.end(); // end inner head-block
 597                 self.end(); // end outer head-block
 598             }
 599             hir::ItemKind::Static(ref ty, m, expr) => {
 600                 self.head(visibility_qualified(&item.vis, "static"));
 601                 if m == hir::Mutability::Mut {
 602                     self.word_space("mut");
 603                 }
 604                 self.print_ident(item.ident);
 605                 self.word_space(":");
 606                 self.print_type(&ty);
 607                 self.s.space();
 608                 self.end(); // end the head-ibox
 609
 610                 self.word_space("=");
 611                 self.ann.nested(self, Nested::Body(expr));
 612                 self.s.word(";");
 613                 self.end(); // end the outer cbox
 614             }
 615             hir::ItemKind::Const(ref ty, expr) => {
 616                 self.head(visibility_qualified(&item.vis, "const"));
 617                 self.print_ident(item.ident);
 618                 self.word_space(":");
 619                 self.print_type(&ty);
 620                 self.s.space();
 621                 self.end(); // end the head-ibox
 622
 623                 self.word_space("=");
 624                 self.ann.nested(self, Nested::Body(expr));
 625                 self.s.word(";");
 626                 self.end(); // end the outer cbox
 627             }
 628             hir::ItemKind::Fn(ref sig, ref param_names, body) => {
 629                 self.head("");
 630                 self.print_fn(
 631                     &sig.decl,
 632                     sig.header,
 633                     Some(item.ident.name),
 634                     param_names,
 635                     &item.vis,
 636                     &[],
 637                     Some(body),
 638                 );
 639                 self.s.word(" ");
 640                 self.end(); // need to close a box
 641                 self.end(); // need to close a box
 642                 self.ann.nested(self, Nested::Body(body));
 643             }
 644             hir::ItemKind::Mod(ref _mod) => {
 645                 self.head(visibility_qualified(&item.vis, "mod"));
 646                 self.print_ident(item.ident);
 647                 self.nbsp();
 648                 self.bopen();
 649                 self.print_mod(_mod, attrs);
 650                 self.bclose(item.span);
 651             }
 652             hir::ItemKind::ForeignMod { abi, items } => {
 653                 self.head("extern");
 654                 self.word_nbsp(abi.to_string());
 655                 self.bopen();
 656                 self.print_inner_attributes(self.attrs(item.hir_id()));
 657                 for item in items {
 658                     self.ann.nested(self, Nested::ForeignItem(item.id));
 659                 }
 660                 self.bclose(item.span);
 661             }
 662             hir::ItemKind::GlobalAsm(ref asm) => {
 663                 self.head(visibility_qualified(&item.vis, "global_asm!"));
 664                 self.print_inline_asm(asm);
 665                 self.end()
 666             }
 667             hir::ItemKind::TyAlias(ref ty, ref generics) => {
 668                 self.print_item_type(item, &generics, |state| {
 669                     state.word_space("=");
 670                     state.print_type(&ty);
 671                 });
 672             }
 673             hir::ItemKind::OpaqueTy(ref opaque_ty) => {
 674                 self.print_item_type(item, &opaque_ty.generics, |state| {
 675                     let mut real_bounds = Vec::with_capacity(opaque_ty.bounds.len());
 676                     for b in opaque_ty.bounds.iter() {
 677                         if let GenericBound::Trait(ref ptr, hir::TraitBoundModifier::Maybe) = *b {
 678                             state.s.space();
 679                             state.word_space("for ?");
 680                             state.print_trait_ref(&ptr.trait_ref);
 681                         } else {
 682                             real_bounds.push(b);
 683                         }
 684                     }
 685                     state.print_bounds("= impl", real_bounds);
 686                 });
 687             }
 688             hir::ItemKind::Enum(ref enum_definition, ref params) => {
 689                 self.print_enum_def(enum_definition, params, item.ident.name, item.span, &item.vis);
 690             }
 691             hir::ItemKind::Struct(ref struct_def, ref generics) => {
 692                 self.head(visibility_qualified(&item.vis, "struct"));
 693                 self.print_struct(struct_def, generics, item.ident.name, item.span, true);
 694             }
 695             hir::ItemKind::Union(ref struct_def, ref generics) => {
 696                 self.head(visibility_qualified(&item.vis, "union"));
 697                 self.print_struct(struct_def, generics, item.ident.name, item.span, true);
 698             }
 699             hir::ItemKind::Impl(hir::Impl {
 700                 unsafety,
 701                 polarity,
 702                 defaultness,
 703                 constness,
 704                 defaultness_span: _,
 705                 ref generics,
 706                 ref of_trait,
 707                 ref self_ty,
 708                 items,
 709             }) => {
 710                 self.head("");
 711                 self.print_visibility(&item.vis);
 712                 self.print_defaultness(defaultness);
 713                 self.print_unsafety(unsafety);
 714                 self.word_nbsp("impl");
 715
 716                 if !generics.params.is_empty() {
 717                     self.print_generic_params(&generics.params);
 718                     self.s.space();
 719                 }
 720
 721                 if constness == hir::Constness::Const {
 722                     self.word_nbsp("const");
 723                 }
 724
 725                 if let hir::ImplPolarity::Negative(_) = polarity {
 726                     self.s.word("!");
 727                 }
 728
 729                 if let Some(ref t) = of_trait {
 730                     self.print_trait_ref(t);
 731                     self.s.space();
 732                     self.word_space("for");
 733                 }
 734
 735                 self.print_type(&self_ty);
 736                 self.print_where_clause(&generics.where_clause);
 737
 738                 self.s.space();
 739                 self.bopen();
 740                 self.print_inner_attributes(attrs);
 741                 for impl_item in items {
 742                     self.ann.nested(self, Nested::ImplItem(impl_item.id));
 743                 }
 744                 self.bclose(item.span);
 745             }
 746             hir::ItemKind::Trait(is_auto, unsafety, ref generics, ref bounds, trait_items) => {
 747                 self.head("");
 748                 self.print_visibility(&item.vis);
 749                 self.print_is_auto(is_auto);
 750                 self.print_unsafety(unsafety);
 751                 self.word_nbsp("trait");
 752                 self.print_ident(item.ident);
 753                 self.print_generic_params(&generics.params);
 754                 let mut real_bounds = Vec::with_capacity(bounds.len());
 755                 for b in bounds.iter() {
 756                     if let GenericBound::Trait(ref ptr, hir::TraitBoundModifier::Maybe) = *b {
 757                         self.s.space();
 758                         self.word_space("for ?");
 759                         self.print_trait_ref(&ptr.trait_ref);
 760                     } else {
 761                         real_bounds.push(b);
 762                     }
 763                 }
 764                 self.print_bounds(":", real_bounds);
 765                 self.print_where_clause(&generics.where_clause);
 766                 self.s.word(" ");
 767                 self.bopen();
 768                 for trait_item in trait_items {
 769                     self.ann.nested(self, Nested::TraitItem(trait_item.id));
 770                 }
 771                 self.bclose(item.span);
 772             }
 773             hir::ItemKind::TraitAlias(ref generics, ref bounds) => {
 774                 self.head("");
 775                 self.print_visibility(&item.vis);
 776                 self.word_nbsp("trait");
 777                 self.print_ident(item.ident);
 778                 self.print_generic_params(&generics.params);
 779                 let mut real_bounds = Vec::with_capacity(bounds.len());
 780                 // FIXME(durka) this seems to be some quite outdated syntax
 781                 for b in bounds.iter() {
 782                     if let GenericBound::Trait(ref ptr, hir::TraitBoundModifier::Maybe) = *b {
 783                         self.s.space();
 784                         self.word_space("for ?");
 785                         self.print_trait_ref(&ptr.trait_ref);
 786                     } else {
 787                         real_bounds.push(b);
 788                     }
 789                 }
 790                 self.nbsp();
 791                 self.print_bounds("=", real_bounds);
 792                 self.print_where_clause(&generics.where_clause);
 793                 self.s.word(";");
 794             }
 795         }
 796         self.ann.post(self, AnnNode::Item(item))
 797     }
 798
 799     pub fn print_trait_ref(&mut self, t: &hir::TraitRef<'_>) {
 800         self.print_path(&t.path, false)
 801     }
 802
 803     fn print_formal_generic_params(&mut self, generic_params: &[hir::GenericParam<'_>]) {
 804         if !generic_params.is_empty() {
 805             self.s.word("for");
 806             self.print_generic_params(generic_params);
 807             self.nbsp();
 808         }
 809     }
 810
 811     fn print_poly_trait_ref(&mut self, t: &hir::PolyTraitRef<'_>) {
 812         self.print_formal_generic_params(&t.bound_generic_params);
 813         self.print_trait_ref(&t.trait_ref)
 814     }
 815
 816     pub fn print_enum_def(
 817         &mut self,
 818         enum_definition: &hir::EnumDef<'_>,
 819         generics: &hir::Generics<'_>,
 820         name: Symbol,
 821         span: rustc_span::Span,
 822         visibility: &hir::Visibility<'_>,
 823     ) {
 824         self.head(visibility_qualified(visibility, "enum"));
 825         self.print_name(name);
 826         self.print_generic_params(&generics.params);
 827         self.print_where_clause(&generics.where_clause);
 828         self.s.space();
 829         self.print_variants(&enum_definition.variants, span)
 830     }
 831
 832     pub fn print_variants(&mut self, variants: &[hir::Variant<'_>], span: rustc_span::Span) {
 833         self.bopen();
 834         for v in variants {
 835             self.space_if_not_bol();
 836             self.maybe_print_comment(v.span.lo());
 837             self.print_outer_attributes(self.attrs(v.id));
 838             self.ibox(INDENT_UNIT);
 839             self.print_variant(v);
 840             self.s.word(",");
 841             self.end();
 842             self.maybe_print_trailing_comment(v.span, None);
 843         }
 844         self.bclose(span)
 845     }
 846
 847     pub fn print_visibility(&mut self, vis: &hir::Visibility<'_>) {
 848         match vis.node {
 849             hir::VisibilityKind::Public => self.word_nbsp("pub"),
 850             hir::VisibilityKind::Crate(ast::CrateSugar::JustCrate) => self.word_nbsp("crate"),
 851             hir::VisibilityKind::Crate(ast::CrateSugar::PubCrate) => self.word_nbsp("pub(crate)"),
 852             hir::VisibilityKind::Restricted { ref path, .. } => {
 853                 self.s.word("pub(");
 854                 if path.segments.len() == 1 && path.segments[0].ident.name == kw::Super {
 855                     // Special case: `super` can print like `pub(super)`.
 856                     self.s.word("super");
 857                 } else {
 858                     // Everything else requires `in` at present.
 859                     self.word_nbsp("in");
 860                     self.print_path(path, false);
 861                 }
 862                 self.word_nbsp(")");
 863             }
 864             hir::VisibilityKind::Inherited => (),
 865         }
 866     }
 867
 868     pub fn print_defaultness(&mut self, defaultness: hir::Defaultness) {
 869         match defaultness {
 870             hir::Defaultness::Default { .. } => self.word_nbsp("default"),
 871             hir::Defaultness::Final => (),
 872         }
 873     }
 874
 875     pub fn print_struct(
 876         &mut self,
 877         struct_def: &hir::VariantData<'_>,
 878         generics: &hir::Generics<'_>,
 879         name: Symbol,
 880         span: rustc_span::Span,
 881         print_finalizer: bool,
 882     ) {
 883         self.print_name(name);
 884         self.print_generic_params(&generics.params);
 885         match struct_def {
 886             hir::VariantData::Tuple(..) | hir::VariantData::Unit(..) => {
 887                 if let hir::VariantData::Tuple(..) = struct_def {
 888                     self.popen();
 889                     self.commasep(Inconsistent, struct_def.fields(), |s, field| {
 890                         s.maybe_print_comment(field.span.lo());
 891                         s.print_outer_attributes(s.attrs(field.hir_id));
 892                         s.print_visibility(&field.vis);
 893                         s.print_type(&field.ty)
 894                     });
 895                     self.pclose();
 896                 }
 897                 self.print_where_clause(&generics.where_clause);
 898                 if print_finalizer {
 899                     self.s.word(";");
 900                 }
 901                 self.end();
 902                 self.end() // close the outer-box
 903             }
 904             hir::VariantData::Struct(..) => {
 905                 self.print_where_clause(&generics.where_clause);
 906                 self.nbsp();
 907                 self.bopen();
 908                 self.hardbreak_if_not_bol();
 909
 910                 for field in struct_def.fields() {
 911                     self.hardbreak_if_not_bol();
 912                     self.maybe_print_comment(field.span.lo());
 913                     self.print_outer_attributes(self.attrs(field.hir_id));
 914                     self.print_visibility(&field.vis);
 915                     self.print_ident(field.ident);
 916                     self.word_nbsp(":");
 917                     self.print_type(&field.ty);
 918                     self.s.word(",");
 919                 }
 920
 921                 self.bclose(span)
 922             }
 923         }
 924     }
 925
 926     pub fn print_variant(&mut self, v: &hir::Variant<'_>) {
 927         self.head("");
 928         let generics = hir::Generics::empty();
 929         self.print_struct(&v.data, &generics, v.ident.name, v.span, false);
 930         if let Some(ref d) = v.disr_expr {
 931             self.s.space();
 932             self.word_space("=");
 933             self.print_anon_const(d);
 934         }
 935     }
 936     pub fn print_method_sig(
 937         &mut self,
 938         ident: Ident,
 939         m: &hir::FnSig<'_>,
 940         generics: &hir::Generics<'_>,
 941         vis: &hir::Visibility<'_>,
 942         arg_names: &[Ident],
 943         body_id: Option<hir::BodyId>,
 944     ) {
 945         self.print_fn(&m.decl, m.header, Some(ident.name), generics, vis, arg_names, body_id)
 946     }
 947
 948     pub fn print_trait_item(&mut self, ti: &hir::TraitItem<'_>) {
 949         self.ann.pre(self, AnnNode::SubItem(ti.hir_id()));
 950         self.hardbreak_if_not_bol();
 951         self.maybe_print_comment(ti.span.lo());
 952         self.print_outer_attributes(self.attrs(ti.hir_id()));
 953         match ti.kind {
 954             hir::TraitItemKind::Const(ref ty, default) => {
 955                 let vis =
 956                     Spanned { span: rustc_span::DUMMY_SP, node: hir::VisibilityKind::Inherited };
 957                 self.print_associated_const(ti.ident, &ty, default, &vis);
 958             }
 959             hir::TraitItemKind::Fn(ref sig, hir::TraitFn::Required(ref arg_names)) => {
 960                 let vis =
 961                     Spanned { span: rustc_span::DUMMY_SP, node: hir::VisibilityKind::Inherited };
 962                 self.print_method_sig(ti.ident, sig, &ti.generics, &vis, arg_names, None);
 963                 self.s.word(";");
 964             }
 965             hir::TraitItemKind::Fn(ref sig, hir::TraitFn::Provided(body)) => {
 966                 let vis =
 967                     Spanned { span: rustc_span::DUMMY_SP, node: hir::VisibilityKind::Inherited };
 968                 self.head("");
 969                 self.print_method_sig(ti.ident, sig, &ti.generics, &vis, &[], Some(body));
 970                 self.nbsp();
 971                 self.end(); // need to close a box
 972                 self.end(); // need to close a box
 973                 self.ann.nested(self, Nested::Body(body));
 974             }
 975             hir::TraitItemKind::Type(ref bounds, ref default) => {
 976                 self.print_associated_type(
 977                     ti.ident,
 978                     &ti.generics,
 979                     Some(bounds),
 980                     default.as_ref().map(|ty| &**ty),
 981                 );
 982             }
 983         }
 984         self.ann.post(self, AnnNode::SubItem(ti.hir_id()))
 985     }
 986
 987     pub fn print_impl_item(&mut self, ii: &hir::ImplItem<'_>) {
 988         self.ann.pre(self, AnnNode::SubItem(ii.hir_id()));
 989         self.hardbreak_if_not_bol();
 990         self.maybe_print_comment(ii.span.lo());
 991         self.print_outer_attributes(self.attrs(ii.hir_id()));
 992         self.print_defaultness(ii.defaultness);
 993
 994         match ii.kind {
 995             hir::ImplItemKind::Const(ref ty, expr) => {
 996                 self.print_associated_const(ii.ident, &ty, Some(expr), &ii.vis);
 997             }
 998             hir::ImplItemKind::Fn(ref sig, body) => {
 999                 self.head("");
1000                 self.print_method_sig(ii.ident, sig, &ii.generics, &ii.vis, &[], Some(body));
1001                 self.nbsp();
1002                 self.end(); // need to close a box
1003                 self.end(); // need to close a box
1004                 self.ann.nested(self, Nested::Body(body));
1005             }
1006             hir::ImplItemKind::TyAlias(ref ty) => {
1007                 self.print_associated_type(ii.ident, &ii.generics, None, Some(ty));
1008             }
1009         }
1010         self.ann.post(self, AnnNode::SubItem(ii.hir_id()))
1011     }
1012
1013     pub fn print_local(&mut self, init: Option<&hir::Expr<'_>>, decl: impl Fn(&mut Self)) {
1014         self.space_if_not_bol();
1015         self.ibox(INDENT_UNIT);
1016         self.word_nbsp("let");
1017
1018         self.ibox(INDENT_UNIT);
1019         decl(self);
1020         self.end();
1021
1022         if let Some(ref init) = init {
1023             self.nbsp();
1024             self.word_space("=");
1025             self.print_expr(&init);
1026         }
1027         self.end()
1028     }
1029
1030     pub fn print_stmt(&mut self, st: &hir::Stmt<'_>) {
1031         self.maybe_print_comment(st.span.lo());
1032         match st.kind {
1033             hir::StmtKind::Local(ref loc) => {
1034                 self.print_local(loc.init.as_deref(), |this| this.print_local_decl(&loc));
1035             }
1036             hir::StmtKind::Item(item) => self.ann.nested(self, Nested::Item(item)),
1037             hir::StmtKind::Expr(ref expr) => {
1038                 self.space_if_not_bol();
1039                 self.print_expr(&expr);
1040             }
1041             hir::StmtKind::Semi(ref expr) => {
1042                 self.space_if_not_bol();
1043                 self.print_expr(&expr);
1044                 self.s.word(";");
1045             }
1046         }
1047         if stmt_ends_with_semi(&st.kind) {
1048             self.s.word(";");
1049         }
1050         self.maybe_print_trailing_comment(st.span, None)
1051     }
1052
1053     pub fn print_block(&mut self, blk: &hir::Block<'_>) {
1054         self.print_block_with_attrs(blk, &[])
1055     }
1056
1057     pub fn print_block_unclosed(&mut self, blk: &hir::Block<'_>) {
1058         self.print_block_maybe_unclosed(blk, &[], false)
1059     }
1060
1061     pub fn print_block_with_attrs(&mut self, blk: &hir::Block<'_>, attrs: &[ast::Attribute]) {
1062         self.print_block_maybe_unclosed(blk, attrs, true)
1063     }
1064
1065     pub fn print_block_maybe_unclosed(
1066         &mut self,
1067         blk: &hir::Block<'_>,
1068         attrs: &[ast::Attribute],
1069         close_box: bool,
1070     ) {
1071         match blk.rules {
1072             hir::BlockCheckMode::UnsafeBlock(..) => self.word_space("unsafe"),
1073             hir::BlockCheckMode::DefaultBlock => (),
1074         }
1075         self.maybe_print_comment(blk.span.lo());
1076         self.ann.pre(self, AnnNode::Block(blk));
1077         self.bopen();
1078
1079         self.print_inner_attributes(attrs);
1080
1081         for st in blk.stmts {
1082             self.print_stmt(st);
1083         }
1084         if let Some(ref expr) = blk.expr {
1085             self.space_if_not_bol();
1086             self.print_expr(&expr);
1087             self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi()));
1088         }
1089         self.bclose_maybe_open(blk.span, close_box);
1090         self.ann.post(self, AnnNode::Block(blk))
1091     }
1092
1093     fn print_else(&mut self, els: Option<&hir::Expr<'_>>) {
1094         match els {
1095             Some(else_) => {
1096                 match else_.kind {
1097                     // "another else-if"
1098                     hir::ExprKind::If(ref i, ref then, ref e) => {
1099                         self.cbox(INDENT_UNIT - 1);
1100                         self.ibox(0);
1101                         self.s.word(" else if ");
1102                         self.print_expr_as_cond(&i);
1103                         self.s.space();
1104                         self.print_expr(&then);
1105                         self.print_else(e.as_ref().map(|e| &**e))
1106                     }
1107                     // "final else"
1108                     hir::ExprKind::Block(ref b, _) => {
1109                         self.cbox(INDENT_UNIT - 1);
1110                         self.ibox(0);
1111                         self.s.word(" else ");
1112                         self.print_block(&b)
1113                     }
1114                     hir::ExprKind::Match(ref expr, arms, _) => {
1115                         // else if let desugared to match
1116                         assert!(arms.len() == 2, "if let desugars to match with two arms");
1117
1118                         self.s.word(" else ");
1119                         self.s.word("{");
1120
1121                         self.cbox(INDENT_UNIT);
1122                         self.ibox(INDENT_UNIT);
1123                         self.word_nbsp("match");
1124                         self.print_expr_as_cond(&expr);
1125                         self.s.space();
1126                         self.bopen();
1127                         for arm in arms {
1128                             self.print_arm(arm);
1129                         }
1130                         self.bclose(expr.span);
1131
1132                         self.s.word("}");
1133                     }
1134                     // BLEAH, constraints would be great here
1135                     _ => {
1136                         panic!("print_if saw if with weird alternative");
1137                     }
1138                 }
1139             }
1140             _ => {}
1141         }
1142     }
1143
1144     pub fn print_if(
1145         &mut self,
1146         test: &hir::Expr<'_>,
1147         blk: &hir::Expr<'_>,
1148         elseopt: Option<&hir::Expr<'_>>,
1149     ) {
1150         self.head("if");
1151         self.print_expr_as_cond(test);
1152         self.s.space();
1153         self.print_expr(blk);
1154         self.print_else(elseopt)
1155     }
1156
1157     pub fn print_anon_const(&mut self, constant: &hir::AnonConst) {
1158         self.ann.nested(self, Nested::Body(constant.body))
1159     }
1160
1161     fn print_call_post(&mut self, args: &[hir::Expr<'_>]) {
1162         self.popen();
1163         self.commasep_exprs(Inconsistent, args);
1164         self.pclose()
1165     }
1166
1167     pub fn print_expr_maybe_paren(&mut self, expr: &hir::Expr<'_>, prec: i8) {
1168         let needs_par = expr.precedence().order() < prec;
1169         if needs_par {
1170             self.popen();
1171         }
1172         self.print_expr(expr);
1173         if needs_par {
1174             self.pclose();
1175         }
1176     }
1177
1178     /// Print an expr using syntax that's acceptable in a condition position, such as the `cond` in
1179     /// `if cond { ... }`.
1180     pub fn print_expr_as_cond(&mut self, expr: &hir::Expr<'_>) {
1181         let needs_par = match expr.kind {
1182             // These cases need parens due to the parse error observed in #26461: `if return {}`
1183             // parses as the erroneous construct `if (return {})`, not `if (return) {}`.
1184             hir::ExprKind::Closure(..) | hir::ExprKind::Ret(..) | hir::ExprKind::Break(..) => true,
1185
1186             _ => contains_exterior_struct_lit(expr),
1187         };
1188
1189         if needs_par {
1190             self.popen();
1191         }
1192         self.print_expr(expr);
1193         if needs_par {
1194             self.pclose();
1195         }
1196     }
1197
1198     fn print_expr_vec(&mut self, exprs: &[hir::Expr<'_>]) {
1199         self.ibox(INDENT_UNIT);
1200         self.s.word("[");
1201         self.commasep_exprs(Inconsistent, exprs);
1202         self.s.word("]");
1203         self.end()
1204     }
1205
1206     fn print_expr_anon_const(&mut self, anon_const: &hir::AnonConst) {
1207         self.ibox(INDENT_UNIT);
1208         self.s.word_space("const");
1209         self.print_anon_const(anon_const);
1210         self.end()
1211     }
1212
1213     fn print_expr_repeat(&mut self, element: &hir::Expr<'_>, count: &hir::AnonConst) {
1214         self.ibox(INDENT_UNIT);
1215         self.s.word("[");
1216         self.print_expr(element);
1217         self.word_space(";");
1218         self.print_anon_const(count);
1219         self.s.word("]");
1220         self.end()
1221     }
1222
1223     fn print_expr_struct(
1224         &mut self,
1225         qpath: &hir::QPath<'_>,
1226         fields: &[hir::ExprField<'_>],
1227         wth: &Option<&hir::Expr<'_>>,
1228     ) {
1229         self.print_qpath(qpath, true);
1230         self.s.word("{");
1231         self.commasep_cmnt(
1232             Consistent,
1233             fields,
1234             |s, field| {
1235                 s.ibox(INDENT_UNIT);
1236                 if !field.is_shorthand {
1237                     s.print_ident(field.ident);
1238                     s.word_space(":");
1239                 }
1240                 s.print_expr(&field.expr);
1241                 s.end()
1242             },
1243             |f| f.span,
1244         );
1245         match *wth {
1246             Some(ref expr) => {
1247                 self.ibox(INDENT_UNIT);
1248                 if !fields.is_empty() {
1249                     self.s.word(",");
1250                     self.s.space();
1251                 }
1252                 self.s.word("..");
1253                 self.print_expr(&expr);
1254                 self.end();
1255             }
1256             _ => {
1257                 if !fields.is_empty() {
1258                     self.s.word(",")
1259                 }
1260             }
1261         }
1262         self.s.word("}");
1263     }
1264
1265     fn print_expr_tup(&mut self, exprs: &[hir::Expr<'_>]) {
1266         self.popen();
1267         self.commasep_exprs(Inconsistent, exprs);
1268         if exprs.len() == 1 {
1269             self.s.word(",");
1270         }
1271         self.pclose()
1272     }
1273
1274     fn print_expr_call(&mut self, func: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
1275         let prec = match func.kind {
1276             hir::ExprKind::Field(..) => parser::PREC_FORCE_PAREN,
1277             _ => parser::PREC_POSTFIX,
1278         };
1279
1280         self.print_expr_maybe_paren(func, prec);
1281         self.print_call_post(args)
1282     }
1283
1284     fn print_expr_method_call(&mut self, segment: &hir::PathSegment<'_>, args: &[hir::Expr<'_>]) {
1285         let base_args = &args[1..];
1286         self.print_expr_maybe_paren(&args[0], parser::PREC_POSTFIX);
1287         self.s.word(".");
1288         self.print_ident(segment.ident);
1289
1290         let generic_args = segment.args();
1291         if !generic_args.args.is_empty() || !generic_args.bindings.is_empty() {
1292             self.print_generic_args(generic_args, segment.infer_args, true);
1293         }
1294
1295         self.print_call_post(base_args)
1296     }
1297
1298     fn print_expr_binary(&mut self, op: hir::BinOp, lhs: &hir::Expr<'_>, rhs: &hir::Expr<'_>) {
1299         let assoc_op = bin_op_to_assoc_op(op.node);
1300         let prec = assoc_op.precedence() as i8;
1301         let fixity = assoc_op.fixity();
1302
1303         let (left_prec, right_prec) = match fixity {
1304             Fixity::Left => (prec, prec + 1),
1305             Fixity::Right => (prec + 1, prec),
1306             Fixity::None => (prec + 1, prec + 1),
1307         };
1308
1309         let left_prec = match (&lhs.kind, op.node) {
1310             // These cases need parens: `x as i32 < y` has the parser thinking that `i32 < y` is
1311             // the beginning of a path type. It starts trying to parse `x as (i32 < y ...` instead
1312             // of `(x as i32) < ...`. We need to convince it _not_ to do that.
1313             (&hir::ExprKind::Cast { .. }, hir::BinOpKind::Lt | hir::BinOpKind::Shl) => {
1314                 parser::PREC_FORCE_PAREN
1315             }
1316             _ => left_prec,
1317         };
1318
1319         self.print_expr_maybe_paren(lhs, left_prec);
1320         self.s.space();
1321         self.word_space(op.node.as_str());
1322         self.print_expr_maybe_paren(rhs, right_prec)
1323     }
1324
1325     fn print_expr_unary(&mut self, op: hir::UnOp, expr: &hir::Expr<'_>) {
1326         self.s.word(op.as_str());
1327         self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
1328     }
1329
1330     fn print_expr_addr_of(
1331         &mut self,
1332         kind: hir::BorrowKind,
1333         mutability: hir::Mutability,
1334         expr: &hir::Expr<'_>,
1335     ) {
1336         self.s.word("&");
1337         match kind {
1338             hir::BorrowKind::Ref => self.print_mutability(mutability, false),
1339             hir::BorrowKind::Raw => {
1340                 self.word_nbsp("raw");
1341                 self.print_mutability(mutability, true);
1342             }
1343         }
1344         self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
1345     }
1346
1347     fn print_literal(&mut self, lit: &hir::Lit) {
1348         self.maybe_print_comment(lit.span.lo());
1349         self.word(lit.node.to_lit_token().to_string())
1350     }
1351
1352     fn print_inline_asm(&mut self, asm: &hir::InlineAsm<'_>) {
1353         enum AsmArg<'a> {
1354             Template(String),
1355             Operand(&'a hir::InlineAsmOperand<'a>),
1356             Options(ast::InlineAsmOptions),
1357         }
1358
1359         let mut args = vec![];
1360         args.push(AsmArg::Template(ast::InlineAsmTemplatePiece::to_string(&asm.template)));
1361         args.extend(asm.operands.iter().map(|(o, _)| AsmArg::Operand(o)));
1362         if !asm.options.is_empty() {
1363             args.push(AsmArg::Options(asm.options));
1364         }
1365
1366         self.popen();
1367         self.commasep(Consistent, &args, |s, arg| match arg {
1368             AsmArg::Template(template) => s.print_string(&template, ast::StrStyle::Cooked),
1369             AsmArg::Operand(op) => match op {
1370                 hir::InlineAsmOperand::In { reg, expr } => {
1371                     s.word("in");
1372                     s.popen();
1373                     s.word(format!("{}", reg));
1374                     s.pclose();
1375                     s.space();
1376                     s.print_expr(expr);
1377                 }
1378                 hir::InlineAsmOperand::Out { reg, late, expr } => {
1379                     s.word(if *late { "lateout" } else { "out" });
1380                     s.popen();
1381                     s.word(format!("{}", reg));
1382                     s.pclose();
1383                     s.space();
1384                     match expr {
1385                         Some(expr) => s.print_expr(expr),
1386                         None => s.word("_"),
1387                     }
1388                 }
1389                 hir::InlineAsmOperand::InOut { reg, late, expr } => {
1390                     s.word(if *late { "inlateout" } else { "inout" });
1391                     s.popen();
1392                     s.word(format!("{}", reg));
1393                     s.pclose();
1394                     s.space();
1395                     s.print_expr(expr);
1396                 }
1397                 hir::InlineAsmOperand::SplitInOut { reg, late, in_expr, out_expr } => {
1398                     s.word(if *late { "inlateout" } else { "inout" });
1399                     s.popen();
1400                     s.word(format!("{}", reg));
1401                     s.pclose();
1402                     s.space();
1403                     s.print_expr(in_expr);
1404                     s.space();
1405                     s.word_space("=>");
1406                     match out_expr {
1407                         Some(out_expr) => s.print_expr(out_expr),
1408                         None => s.word("_"),
1409                     }
1410                 }
1411                 hir::InlineAsmOperand::Const { anon_const } => {
1412                     s.word("const");
1413                     s.space();
1414                     s.print_anon_const(anon_const);
1415                 }
1416                 hir::InlineAsmOperand::Sym { expr } => {
1417                     s.word("sym");
1418                     s.space();
1419                     s.print_expr(expr);
1420                 }
1421             },
1422             AsmArg::Options(opts) => {
1423                 s.word("options");
1424                 s.popen();
1425                 let mut options = vec![];
1426                 if opts.contains(ast::InlineAsmOptions::PURE) {
1427                     options.push("pure");
1428                 }
1429                 if opts.contains(ast::InlineAsmOptions::NOMEM) {
1430                     options.push("nomem");
1431                 }
1432                 if opts.contains(ast::InlineAsmOptions::READONLY) {
1433                     options.push("readonly");
1434                 }
1435                 if opts.contains(ast::InlineAsmOptions::PRESERVES_FLAGS) {
1436                     options.push("preserves_flags");
1437                 }
1438                 if opts.contains(ast::InlineAsmOptions::NORETURN) {
1439                     options.push("noreturn");
1440                 }
1441                 if opts.contains(ast::InlineAsmOptions::NOSTACK) {
1442                     options.push("nostack");
1443                 }
1444                 if opts.contains(ast::InlineAsmOptions::ATT_SYNTAX) {
1445                     options.push("att_syntax");
1446                 }
1447                 if opts.contains(ast::InlineAsmOptions::RAW) {
1448                     options.push("raw");
1449                 }
1450                 s.commasep(Inconsistent, &options, |s, &opt| {
1451                     s.word(opt);
1452                 });
1453                 s.pclose();
1454             }
1455         });
1456         self.pclose();
1457     }
1458
1459     pub fn print_expr(&mut self, expr: &hir::Expr<'_>) {
1460         self.maybe_print_comment(expr.span.lo());
1461         self.print_outer_attributes(self.attrs(expr.hir_id));
1462         self.ibox(INDENT_UNIT);
1463         self.ann.pre(self, AnnNode::Expr(expr));
1464         match expr.kind {
1465             hir::ExprKind::Box(ref expr) => {
1466                 self.word_space("box");
1467                 self.print_expr_maybe_paren(expr, parser::PREC_PREFIX);
1468             }
1469             hir::ExprKind::Array(ref exprs) => {
1470                 self.print_expr_vec(exprs);
1471             }
1472             hir::ExprKind::ConstBlock(ref anon_const) => {
1473                 self.print_expr_anon_const(anon_const);
1474             }
1475             hir::ExprKind::Repeat(ref element, ref count) => {
1476                 self.print_expr_repeat(&element, count);
1477             }
1478             hir::ExprKind::Struct(ref qpath, fields, ref wth) => {
1479                 self.print_expr_struct(qpath, fields, wth);
1480             }
1481             hir::ExprKind::Tup(ref exprs) => {
1482                 self.print_expr_tup(exprs);
1483             }
1484             hir::ExprKind::Call(ref func, ref args) => {
1485                 self.print_expr_call(&func, args);
1486             }
1487             hir::ExprKind::MethodCall(ref segment, _, ref args, _) => {
1488                 self.print_expr_method_call(segment, args);
1489             }
1490             hir::ExprKind::Binary(op, ref lhs, ref rhs) => {
1491                 self.print_expr_binary(op, &lhs, &rhs);
1492             }
1493             hir::ExprKind::Unary(op, ref expr) => {
1494                 self.print_expr_unary(op, &expr);
1495             }
1496             hir::ExprKind::AddrOf(k, m, ref expr) => {
1497                 self.print_expr_addr_of(k, m, &expr);
1498             }
1499             hir::ExprKind::Lit(ref lit) => {
1500                 self.print_literal(&lit);
1501             }
1502             hir::ExprKind::Cast(ref expr, ref ty) => {
1503                 let prec = AssocOp::As.precedence() as i8;
1504                 self.print_expr_maybe_paren(&expr, prec);
1505                 self.s.space();
1506                 self.word_space("as");
1507                 self.print_type(&ty);
1508             }
1509             hir::ExprKind::Type(ref expr, ref ty) => {
1510                 let prec = AssocOp::Colon.precedence() as i8;
1511                 self.print_expr_maybe_paren(&expr, prec);
1512                 self.word_space(":");
1513                 self.print_type(&ty);
1514             }
1515             hir::ExprKind::DropTemps(ref init) => {
1516                 // Print `{`:
1517                 self.cbox(INDENT_UNIT);
1518                 self.ibox(0);
1519                 self.bopen();
1520
1521                 // Print `let _t = $init;`:
1522                 let temp = Ident::from_str("_t");
1523                 self.print_local(Some(init), |this| this.print_ident(temp));
1524                 self.s.word(";");
1525
1526                 // Print `_t`:
1527                 self.space_if_not_bol();
1528                 self.print_ident(temp);
1529
1530                 // Print `}`:
1531                 self.bclose_maybe_open(expr.span, true);
1532             }
1533             hir::ExprKind::If(ref test, ref blk, ref elseopt) => {
1534                 self.print_if(&test, &blk, elseopt.as_ref().map(|e| &**e));
1535             }
1536             hir::ExprKind::Loop(ref blk, opt_label, _, _) => {
1537                 if let Some(label) = opt_label {
1538                     self.print_ident(label.ident);
1539                     self.word_space(":");
1540                 }
1541                 self.head("loop");
1542                 self.print_block(&blk);
1543             }
1544             hir::ExprKind::Match(ref expr, arms, _) => {
1545                 self.cbox(INDENT_UNIT);
1546                 self.ibox(INDENT_UNIT);
1547                 self.word_nbsp("match");
1548                 self.print_expr_as_cond(&expr);
1549                 self.s.space();
1550                 self.bopen();
1551                 for arm in arms {
1552                     self.print_arm(arm);
1553                 }
1554                 self.bclose(expr.span);
1555             }
1556             hir::ExprKind::Closure(capture_clause, ref decl, body, _fn_decl_span, _gen) => {
1557                 self.print_capture_clause(capture_clause);
1558
1559                 self.print_closure_params(&decl, body);
1560                 self.s.space();
1561
1562                 // This is a bare expression.
1563                 self.ann.nested(self, Nested::Body(body));
1564                 self.end(); // need to close a box
1565
1566                 // A box will be closed by `print_expr`, but we didn't want an overall
1567                 // wrapper so we closed the corresponding opening. so create an
1568                 // empty box to satisfy the close.
1569                 self.ibox(0);
1570             }
1571             hir::ExprKind::Block(ref blk, opt_label) => {
1572                 if let Some(label) = opt_label {
1573                     self.print_ident(label.ident);
1574                     self.word_space(":");
1575                 }
1576                 // containing cbox, will be closed by print-block at `}`
1577                 self.cbox(INDENT_UNIT);
1578                 // head-box, will be closed by print-block after `{`
1579                 self.ibox(0);
1580                 self.print_block(&blk);
1581             }
1582             hir::ExprKind::Assign(ref lhs, ref rhs, _) => {
1583                 let prec = AssocOp::Assign.precedence() as i8;
1584                 self.print_expr_maybe_paren(&lhs, prec + 1);
1585                 self.s.space();
1586                 self.word_space("=");
1587                 self.print_expr_maybe_paren(&rhs, prec);
1588             }
1589             hir::ExprKind::AssignOp(op, ref lhs, ref rhs) => {
1590                 let prec = AssocOp::Assign.precedence() as i8;
1591                 self.print_expr_maybe_paren(&lhs, prec + 1);
1592                 self.s.space();
1593                 self.s.word(op.node.as_str());
1594                 self.word_space("=");
1595                 self.print_expr_maybe_paren(&rhs, prec);
1596             }
1597             hir::ExprKind::Field(ref expr, ident) => {
1598                 self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX);
1599                 self.s.word(".");
1600                 self.print_ident(ident);
1601             }
1602             hir::ExprKind::Index(ref expr, ref index) => {
1603                 self.print_expr_maybe_paren(&expr, parser::PREC_POSTFIX);
1604                 self.s.word("[");
1605                 self.print_expr(&index);
1606                 self.s.word("]");
1607             }
1608             hir::ExprKind::Path(ref qpath) => self.print_qpath(qpath, true),
1609             hir::ExprKind::Break(destination, ref opt_expr) => {
1610                 self.s.word("break");
1611                 self.s.space();
1612                 if let Some(label) = destination.label {
1613                     self.print_ident(label.ident);
1614                     self.s.space();
1615                 }
1616                 if let Some(ref expr) = *opt_expr {
1617                     self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
1618                     self.s.space();
1619                 }
1620             }
1621             hir::ExprKind::Continue(destination) => {
1622                 self.s.word("continue");
1623                 self.s.space();
1624                 if let Some(label) = destination.label {
1625                     self.print_ident(label.ident);
1626                     self.s.space()
1627                 }
1628             }
1629             hir::ExprKind::Ret(ref result) => {
1630                 self.s.word("return");
1631                 if let Some(ref expr) = *result {
1632                     self.s.word(" ");
1633                     self.print_expr_maybe_paren(&expr, parser::PREC_JUMP);
1634                 }
1635             }
1636             hir::ExprKind::InlineAsm(ref asm) => {
1637                 self.word("asm!");
1638                 self.print_inline_asm(asm);
1639             }
1640             hir::ExprKind::LlvmInlineAsm(ref a) => {
1641                 let i = &a.inner;
1642                 self.s.word("llvm_asm!");
1643                 self.popen();
1644                 self.print_symbol(i.asm, i.asm_str_style);
1645                 self.word_space(":");
1646
1647                 let mut out_idx = 0;
1648                 self.commasep(Inconsistent, &i.outputs, |s, out| {
1649                     let constraint = out.constraint.as_str();
1650                     let mut ch = constraint.chars();
1651                     match ch.next() {
1652                         Some('=') if out.is_rw => {
1653                             s.print_string(&format!("+{}", ch.as_str()), ast::StrStyle::Cooked)
1654                         }
1655                         _ => s.print_string(&constraint, ast::StrStyle::Cooked),
1656                     }
1657                     s.popen();
1658                     s.print_expr(&a.outputs_exprs[out_idx]);
1659                     s.pclose();
1660                     out_idx += 1;
1661                 });
1662                 self.s.space();
1663                 self.word_space(":");
1664
1665                 let mut in_idx = 0;
1666                 self.commasep(Inconsistent, &i.inputs, |s, &co| {
1667                     s.print_symbol(co, ast::StrStyle::Cooked);
1668                     s.popen();
1669                     s.print_expr(&a.inputs_exprs[in_idx]);
1670                     s.pclose();
1671                     in_idx += 1;
1672                 });
1673                 self.s.space();
1674                 self.word_space(":");
1675
1676                 self.commasep(Inconsistent, &i.clobbers, |s, &co| {
1677                     s.print_symbol(co, ast::StrStyle::Cooked);
1678                 });
1679
1680                 let mut options = vec![];
1681                 if i.volatile {
1682                     options.push("volatile");
1683                 }
1684                 if i.alignstack {
1685                     options.push("alignstack");
1686                 }
1687                 if i.dialect == ast::LlvmAsmDialect::Intel {
1688                     options.push("intel");
1689                 }
1690
1691                 if !options.is_empty() {
1692                     self.s.space();
1693                     self.word_space(":");
1694                     self.commasep(Inconsistent, &options, |s, &co| {
1695                         s.print_string(co, ast::StrStyle::Cooked);
1696                     });
1697                 }
1698
1699                 self.pclose();
1700             }
1701             hir::ExprKind::Yield(ref expr, _) => {
1702                 self.word_space("yield");
1703                 self.print_expr_maybe_paren(&expr, parser::PREC_JUMP);
1704             }
1705             hir::ExprKind::Err => {
1706                 self.popen();
1707                 self.s.word("/*ERROR*/");
1708                 self.pclose();
1709             }
1710         }
1711         self.ann.post(self, AnnNode::Expr(expr));
1712         self.end()
1713     }
1714
1715     pub fn print_local_decl(&mut self, loc: &hir::Local<'_>) {
1716         self.print_pat(&loc.pat);
1717         if let Some(ref ty) = loc.ty {
1718             self.word_space(":");
1719             self.print_type(&ty);
1720         }
1721     }
1722
1723     pub fn print_name(&mut self, name: Symbol) {
1724         self.print_ident(Ident::with_dummy_span(name))
1725     }
1726
1727     pub fn print_path(&mut self, path: &hir::Path<'_>, colons_before_params: bool) {
1728         self.maybe_print_comment(path.span.lo());
1729
1730         for (i, segment) in path.segments.iter().enumerate() {
1731             if i > 0 {
1732                 self.s.word("::")
1733             }
1734             if segment.ident.name != kw::PathRoot {
1735                 self.print_ident(segment.ident);
1736                 self.print_generic_args(segment.args(), segment.infer_args, colons_before_params);
1737             }
1738         }
1739     }
1740
1741     pub fn print_path_segment(&mut self, segment: &hir::PathSegment<'_>) {
1742         if segment.ident.name != kw::PathRoot {
1743             self.print_ident(segment.ident);
1744             self.print_generic_args(segment.args(), segment.infer_args, false);
1745         }
1746     }
1747
1748     pub fn print_qpath(&mut self, qpath: &hir::QPath<'_>, colons_before_params: bool) {
1749         match *qpath {
1750             hir::QPath::Resolved(None, ref path) => self.print_path(path, colons_before_params),
1751             hir::QPath::Resolved(Some(ref qself), ref path) => {
1752                 self.s.word("<");
1753                 self.print_type(qself);
1754                 self.s.space();
1755                 self.word_space("as");
1756
1757                 for (i, segment) in path.segments[..path.segments.len() - 1].iter().enumerate() {
1758                     if i > 0 {
1759                         self.s.word("::")
1760                     }
1761                     if segment.ident.name != kw::PathRoot {
1762                         self.print_ident(segment.ident);
1763                         self.print_generic_args(
1764                             segment.args(),
1765                             segment.infer_args,
1766                             colons_before_params,
1767                         );
1768                     }
1769                 }
1770
1771                 self.s.word(">");
1772                 self.s.word("::");
1773                 let item_segment = path.segments.last().unwrap();
1774                 self.print_ident(item_segment.ident);
1775                 self.print_generic_args(
1776                     item_segment.args(),
1777                     item_segment.infer_args,
1778                     colons_before_params,
1779                 )
1780             }
1781             hir::QPath::TypeRelative(ref qself, ref item_segment) => {
1782                 // If we've got a compound-qualified-path, let's push an additional pair of angle
1783                 // brackets, so that we pretty-print `<<A::B>::C>` as `<A::B>::C`, instead of just
1784                 // `A::B::C` (since the latter could be ambiguous to the user)
1785                 if let hir::TyKind::Path(hir::QPath::Resolved(None, _)) = &qself.kind {
1786                     self.print_type(qself);
1787                 } else {
1788                     self.s.word("<");
1789                     self.print_type(qself);
1790                     self.s.word(">");
1791                 }
1792
1793                 self.s.word("::");
1794                 self.print_ident(item_segment.ident);
1795                 self.print_generic_args(
1796                     item_segment.args(),
1797                     item_segment.infer_args,
1798                     colons_before_params,
1799                 )
1800             }
1801             hir::QPath::LangItem(lang_item, span) => {
1802                 self.s.word("#[lang = \"");
1803                 self.print_ident(Ident::new(lang_item.name(), span));
1804                 self.s.word("\"]");
1805             }
1806         }
1807     }
1808
1809     fn print_generic_args(
1810         &mut self,
1811         generic_args: &hir::GenericArgs<'_>,
1812         infer_args: bool,
1813         colons_before_params: bool,
1814     ) {
1815         if generic_args.parenthesized {
1816             self.s.word("(");
1817             self.commasep(Inconsistent, generic_args.inputs(), |s, ty| s.print_type(&ty));
1818             self.s.word(")");
1819
1820             self.space_if_not_bol();
1821             self.word_space("->");
1822             self.print_type(generic_args.bindings[0].ty());
1823         } else {
1824             let start = if colons_before_params { "::<" } else { "<" };
1825             let empty = Cell::new(true);
1826             let start_or_comma = |this: &mut Self| {
1827                 if empty.get() {
1828                     empty.set(false);
1829                     this.s.word(start)
1830                 } else {
1831                     this.word_space(",")
1832                 }
1833             };
1834
1835             let mut nonelided_generic_args: bool = false;
1836             let elide_lifetimes = generic_args.args.iter().all(|arg| match arg {
1837                 GenericArg::Lifetime(lt) => lt.is_elided(),
1838                 _ => {
1839                     nonelided_generic_args = true;
1840                     true
1841                 }
1842             });
1843
1844             if nonelided_generic_args {
1845                 start_or_comma(self);
1846                 self.commasep(
1847                     Inconsistent,
1848                     &generic_args.args,
1849                     |s, generic_arg| match generic_arg {
1850                         GenericArg::Lifetime(lt) if !elide_lifetimes => s.print_lifetime(lt),
1851                         GenericArg::Lifetime(_) => {}
1852                         GenericArg::Type(ty) => s.print_type(ty),
1853                         GenericArg::Const(ct) => s.print_anon_const(&ct.value),
1854                     },
1855                 );
1856             }
1857
1858             // FIXME(eddyb): this would leak into error messages (e.g.,
1859             // "non-exhaustive patterns: `Some::<..>(_)` not covered").
1860             if infer_args && false {
1861                 start_or_comma(self);
1862                 self.s.word("..");
1863             }
1864
1865             for binding in generic_args.bindings.iter() {
1866                 start_or_comma(self);
1867                 self.print_ident(binding.ident);
1868                 self.print_generic_args(binding.gen_args, false, false);
1869                 self.s.space();
1870                 match generic_args.bindings[0].kind {
1871                     hir::TypeBindingKind::Equality { ref ty } => {
1872                         self.word_space("=");
1873                         self.print_type(ty);
1874                     }
1875                     hir::TypeBindingKind::Constraint { bounds } => {
1876                         self.print_bounds(":", bounds);
1877                     }
1878                 }
1879             }
1880
1881             if !empty.get() {
1882                 self.s.word(">")
1883             }
1884         }
1885     }
1886
1887     pub fn print_pat(&mut self, pat: &hir::Pat<'_>) {
1888         self.maybe_print_comment(pat.span.lo());
1889         self.ann.pre(self, AnnNode::Pat(pat));
1890         // Pat isn't normalized, but the beauty of it
1891         // is that it doesn't matter
1892         match pat.kind {
1893             PatKind::Wild => self.s.word("_"),
1894             PatKind::Binding(binding_mode, _, ident, ref sub) => {
1895                 match binding_mode {
1896                     hir::BindingAnnotation::Ref => {
1897                         self.word_nbsp("ref");
1898                         self.print_mutability(hir::Mutability::Not, false);
1899                     }
1900                     hir::BindingAnnotation::RefMut => {
1901                         self.word_nbsp("ref");
1902                         self.print_mutability(hir::Mutability::Mut, false);
1903                     }
1904                     hir::BindingAnnotation::Unannotated => {}
1905                     hir::BindingAnnotation::Mutable => {
1906                         self.word_nbsp("mut");
1907                     }
1908                 }
1909                 self.print_ident(ident);
1910                 if let Some(ref p) = *sub {
1911                     self.s.word("@");
1912                     self.print_pat(&p);
1913                 }
1914             }
1915             PatKind::TupleStruct(ref qpath, ref elts, ddpos) => {
1916                 self.print_qpath(qpath, true);
1917                 self.popen();
1918                 if let Some(ddpos) = ddpos {
1919                     self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(&p));
1920                     if ddpos != 0 {
1921                         self.word_space(",");
1922                     }
1923                     self.s.word("..");
1924                     if ddpos != elts.len() {
1925                         self.s.word(",");
1926                         self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(&p));
1927                     }
1928                 } else {
1929                     self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(&p));
1930                 }
1931                 self.pclose();
1932             }
1933             PatKind::Path(ref qpath) => {
1934                 self.print_qpath(qpath, true);
1935             }
1936             PatKind::Struct(ref qpath, ref fields, etc) => {
1937                 self.print_qpath(qpath, true);
1938                 self.nbsp();
1939                 self.word_space("{");
1940                 self.commasep_cmnt(
1941                     Consistent,
1942                     &fields[..],
1943                     |s, f| {
1944                         s.cbox(INDENT_UNIT);
1945                         if !f.is_shorthand {
1946                             s.print_ident(f.ident);
1947                             s.word_nbsp(":");
1948                         }
1949                         s.print_pat(&f.pat);
1950                         s.end()
1951                     },
1952                     |f| f.pat.span,
1953                 );
1954                 if etc {
1955                     if !fields.is_empty() {
1956                         self.word_space(",");
1957                     }
1958                     self.s.word("..");
1959                 }
1960                 self.s.space();
1961                 self.s.word("}");
1962             }
1963             PatKind::Or(ref pats) => {
1964                 self.strsep("|", true, Inconsistent, &pats[..], |s, p| s.print_pat(&p));
1965             }
1966             PatKind::Tuple(ref elts, ddpos) => {
1967                 self.popen();
1968                 if let Some(ddpos) = ddpos {
1969                     self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(&p));
1970                     if ddpos != 0 {
1971                         self.word_space(",");
1972                     }
1973                     self.s.word("..");
1974                     if ddpos != elts.len() {
1975                         self.s.word(",");
1976                         self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(&p));
1977                     }
1978                 } else {
1979                     self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(&p));
1980                     if elts.len() == 1 {
1981                         self.s.word(",");
1982                     }
1983                 }
1984                 self.pclose();
1985             }
1986             PatKind::Box(ref inner) => {
1987                 let is_range_inner = matches!(inner.kind, PatKind::Range(..));
1988                 self.s.word("box ");
1989                 if is_range_inner {
1990                     self.popen();
1991                 }
1992                 self.print_pat(&inner);
1993                 if is_range_inner {
1994                     self.pclose();
1995                 }
1996             }
1997             PatKind::Ref(ref inner, mutbl) => {
1998                 let is_range_inner = matches!(inner.kind, PatKind::Range(..));
1999                 self.s.word("&");
2000                 self.s.word(mutbl.prefix_str());
2001                 if is_range_inner {
2002                     self.popen();
2003                 }
2004                 self.print_pat(&inner);
2005                 if is_range_inner {
2006                     self.pclose();
2007                 }
2008             }
2009             PatKind::Lit(ref e) => self.print_expr(&e),
2010             PatKind::Range(ref begin, ref end, ref end_kind) => {
2011                 if let Some(expr) = begin {
2012                     self.print_expr(expr);
2013                     self.s.space();
2014                 }
2015                 match *end_kind {
2016                     RangeEnd::Included => self.s.word("..."),
2017                     RangeEnd::Excluded => self.s.word(".."),
2018                 }
2019                 if let Some(expr) = end {
2020                     self.print_expr(expr);
2021                 }
2022             }
2023             PatKind::Slice(ref before, ref slice, ref after) => {
2024                 self.s.word("[");
2025                 self.commasep(Inconsistent, &before[..], |s, p| s.print_pat(&p));
2026                 if let Some(ref p) = *slice {
2027                     if !before.is_empty() {
2028                         self.word_space(",");
2029                     }
2030                     if let PatKind::Wild = p.kind {
2031                         // Print nothing.
2032                     } else {
2033                         self.print_pat(&p);
2034                     }
2035                     self.s.word("..");
2036                     if !after.is_empty() {
2037                         self.word_space(",");
2038                     }
2039                 }
2040                 self.commasep(Inconsistent, &after[..], |s, p| s.print_pat(&p));
2041                 self.s.word("]");
2042             }
2043         }
2044         self.ann.post(self, AnnNode::Pat(pat))
2045     }
2046
2047     pub fn print_param(&mut self, arg: &hir::Param<'_>) {
2048         self.print_outer_attributes(self.attrs(arg.hir_id));
2049         self.print_pat(&arg.pat);
2050     }
2051
2052     pub fn print_arm(&mut self, arm: &hir::Arm<'_>) {
2053         // I have no idea why this check is necessary, but here it
2054         // is :(
2055         if self.attrs(arm.hir_id).is_empty() {
2056             self.s.space();
2057         }
2058         self.cbox(INDENT_UNIT);
2059         self.ann.pre(self, AnnNode::Arm(arm));
2060         self.ibox(0);
2061         self.print_outer_attributes(&self.attrs(arm.hir_id));
2062         self.print_pat(&arm.pat);
2063         self.s.space();
2064         if let Some(ref g) = arm.guard {
2065             match g {
2066                 hir::Guard::If(e) => {
2067                     self.word_space("if");
2068                     self.print_expr(&e);
2069                     self.s.space();
2070                 }
2071                 hir::Guard::IfLet(pat, e) => {
2072                     self.word_nbsp("if");
2073                     self.word_nbsp("let");
2074                     self.print_pat(&pat);
2075                     self.s.space();
2076                     self.word_space("=");
2077                     self.print_expr(&e);
2078                     self.s.space();
2079                 }
2080             }
2081         }
2082         self.word_space("=>");
2083
2084         match arm.body.kind {
2085             hir::ExprKind::Block(ref blk, opt_label) => {
2086                 if let Some(label) = opt_label {
2087                     self.print_ident(label.ident);
2088                     self.word_space(":");
2089                 }
2090                 // the block will close the pattern's ibox
2091                 self.print_block_unclosed(&blk);
2092
2093                 // If it is a user-provided unsafe block, print a comma after it
2094                 if let hir::BlockCheckMode::UnsafeBlock(hir::UnsafeSource::UserProvided) = blk.rules
2095                 {
2096                     self.s.word(",");
2097                 }
2098             }
2099             _ => {
2100                 self.end(); // close the ibox for the pattern
2101                 self.print_expr(&arm.body);
2102                 self.s.word(",");
2103             }
2104         }
2105         self.ann.post(self, AnnNode::Arm(arm));
2106         self.end() // close enclosing cbox
2107     }
2108
2109     pub fn print_fn(
2110         &mut self,
2111         decl: &hir::FnDecl<'_>,
2112         header: hir::FnHeader,
2113         name: Option<Symbol>,
2114         generics: &hir::Generics<'_>,
2115         vis: &hir::Visibility<'_>,
2116         arg_names: &[Ident],
2117         body_id: Option<hir::BodyId>,
2118     ) {
2119         self.print_fn_header_info(header, vis);
2120
2121         if let Some(name) = name {
2122             self.nbsp();
2123             self.print_name(name);
2124         }
2125         self.print_generic_params(&generics.params);
2126
2127         self.popen();
2128         let mut i = 0;
2129         // Make sure we aren't supplied *both* `arg_names` and `body_id`.
2130         assert!(arg_names.is_empty() || body_id.is_none());
2131         self.commasep(Inconsistent, &decl.inputs, |s, ty| {
2132             s.ibox(INDENT_UNIT);
2133             if let Some(arg_name) = arg_names.get(i) {
2134                 s.s.word(arg_name.to_string());
2135                 s.s.word(":");
2136                 s.s.space();
2137             } else if let Some(body_id) = body_id {
2138                 s.ann.nested(s, Nested::BodyParamPat(body_id, i));
2139                 s.s.word(":");
2140                 s.s.space();
2141             }
2142             i += 1;
2143             s.print_type(ty);
2144             s.end()
2145         });
2146         if decl.c_variadic {
2147             self.s.word(", ...");
2148         }
2149         self.pclose();
2150
2151         self.print_fn_output(decl);
2152         self.print_where_clause(&generics.where_clause)
2153     }
2154
2155     fn print_closure_params(&mut self, decl: &hir::FnDecl<'_>, body_id: hir::BodyId) {
2156         self.s.word("|");
2157         let mut i = 0;
2158         self.commasep(Inconsistent, &decl.inputs, |s, ty| {
2159             s.ibox(INDENT_UNIT);
2160
2161             s.ann.nested(s, Nested::BodyParamPat(body_id, i));
2162             i += 1;
2163
2164             if let hir::TyKind::Infer = ty.kind {
2165                 // Print nothing.
2166             } else {
2167                 s.s.word(":");
2168                 s.s.space();
2169                 s.print_type(ty);
2170             }
2171             s.end();
2172         });
2173         self.s.word("|");
2174
2175         if let hir::FnRetTy::DefaultReturn(..) = decl.output {
2176             return;
2177         }
2178
2179         self.space_if_not_bol();
2180         self.word_space("->");
2181         match decl.output {
2182             hir::FnRetTy::Return(ref ty) => {
2183                 self.print_type(&ty);
2184                 self.maybe_print_comment(ty.span.lo())
2185             }
2186             hir::FnRetTy::DefaultReturn(..) => unreachable!(),
2187         }
2188     }
2189
2190     pub fn print_capture_clause(&mut self, capture_clause: hir::CaptureBy) {
2191         match capture_clause {
2192             hir::CaptureBy::Value => self.word_space("move"),
2193             hir::CaptureBy::Ref => {}
2194         }
2195     }
2196
2197     pub fn print_bounds<'b>(
2198         &mut self,
2199         prefix: &'static str,
2200         bounds: impl IntoIterator<Item = &'b hir::GenericBound<'b>>,
2201     ) {
2202         let mut first = true;
2203         for bound in bounds {
2204             if first {
2205                 self.s.word(prefix);
2206             }
2207             if !(first && prefix.is_empty()) {
2208                 self.nbsp();
2209             }
2210             if first {
2211                 first = false;
2212             } else {
2213                 self.word_space("+");
2214             }
2215
2216             match bound {
2217                 GenericBound::Trait(tref, modifier) => {
2218                     if modifier == &TraitBoundModifier::Maybe {
2219                         self.s.word("?");
2220                     }
2221                     self.print_poly_trait_ref(tref);
2222                 }
2223                 GenericBound::LangItemTrait(lang_item, span, ..) => {
2224                     self.s.word("#[lang = \"");
2225                     self.print_ident(Ident::new(lang_item.name(), *span));
2226                     self.s.word("\"]");
2227                 }
2228                 GenericBound::Outlives(lt) => {
2229                     self.print_lifetime(lt);
2230                 }
2231             }
2232         }
2233     }
2234
2235     pub fn print_generic_params(&mut self, generic_params: &[GenericParam<'_>]) {
2236         if !generic_params.is_empty() {
2237             self.s.word("<");
2238
2239             self.commasep(Inconsistent, generic_params, |s, param| s.print_generic_param(param));
2240
2241             self.s.word(">");
2242         }
2243     }
2244
2245     pub fn print_generic_param(&mut self, param: &GenericParam<'_>) {
2246         if let GenericParamKind::Const { .. } = param.kind {
2247             self.word_space("const");
2248         }
2249
2250         self.print_ident(param.name.ident());
2251
2252         match param.kind {
2253             GenericParamKind::Lifetime { .. } => {
2254                 let mut sep = ":";
2255                 for bound in param.bounds {
2256                     match bound {
2257                         GenericBound::Outlives(ref lt) => {
2258                             self.s.word(sep);
2259                             self.print_lifetime(lt);
2260                             sep = "+";
2261                         }
2262                         _ => panic!(),
2263                     }
2264                 }
2265             }
2266             GenericParamKind::Type { ref default, .. } => {
2267                 self.print_bounds(":", param.bounds);
2268                 if let Some(default) = default {
2269                     self.s.space();
2270                     self.word_space("=");
2271                     self.print_type(&default)
2272                 }
2273             }
2274             GenericParamKind::Const { ref ty, ref default } => {
2275                 self.word_space(":");
2276                 self.print_type(ty);
2277                 if let Some(ref default) = default {
2278                     self.s.space();
2279                     self.word_space("=");
2280                     self.print_anon_const(&default)
2281                 }
2282             }
2283         }
2284     }
2285
2286     pub fn print_lifetime(&mut self, lifetime: &hir::Lifetime) {
2287         self.print_ident(lifetime.name.ident())
2288     }
2289
2290     pub fn print_where_clause(&mut self, where_clause: &hir::WhereClause<'_>) {
2291         if where_clause.predicates.is_empty() {
2292             return;
2293         }
2294
2295         self.s.space();
2296         self.word_space("where");
2297
2298         for (i, predicate) in where_clause.predicates.iter().enumerate() {
2299             if i != 0 {
2300                 self.word_space(",");
2301             }
2302
2303             match predicate {
2304                 hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
2305                     bound_generic_params,
2306                     bounded_ty,
2307                     bounds,
2308                     ..
2309                 }) => {
2310                     self.print_formal_generic_params(bound_generic_params);
2311                     self.print_type(&bounded_ty);
2312                     self.print_bounds(":", *bounds);
2313                 }
2314                 hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
2315                     lifetime,
2316                     bounds,
2317                     ..
2318                 }) => {
2319                     self.print_lifetime(lifetime);
2320                     self.s.word(":");
2321
2322                     for (i, bound) in bounds.iter().enumerate() {
2323                         match bound {
2324                             GenericBound::Outlives(lt) => {
2325                                 self.print_lifetime(lt);
2326                             }
2327                             _ => panic!(),
2328                         }
2329
2330                         if i != 0 {
2331                             self.s.word(":");
2332                         }
2333                     }
2334                 }
2335                 hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
2336                     lhs_ty, rhs_ty, ..
2337                 }) => {
2338                     self.print_type(lhs_ty);
2339                     self.s.space();
2340                     self.word_space("=");
2341                     self.print_type(rhs_ty);
2342                 }
2343             }
2344         }
2345     }
2346
2347     pub fn print_mutability(&mut self, mutbl: hir::Mutability, print_const: bool) {
2348         match mutbl {
2349             hir::Mutability::Mut => self.word_nbsp("mut"),
2350             hir::Mutability::Not => {
2351                 if print_const {
2352                     self.word_nbsp("const")
2353                 }
2354             }
2355         }
2356     }
2357
2358     pub fn print_mt(&mut self, mt: &hir::MutTy<'_>, print_const: bool) {
2359         self.print_mutability(mt.mutbl, print_const);
2360         self.print_type(&mt.ty)
2361     }
2362
2363     pub fn print_fn_output(&mut self, decl: &hir::FnDecl<'_>) {
2364         if let hir::FnRetTy::DefaultReturn(..) = decl.output {
2365             return;
2366         }
2367
2368         self.space_if_not_bol();
2369         self.ibox(INDENT_UNIT);
2370         self.word_space("->");
2371         match decl.output {
2372             hir::FnRetTy::DefaultReturn(..) => unreachable!(),
2373             hir::FnRetTy::Return(ref ty) => self.print_type(&ty),
2374         }
2375         self.end();
2376
2377         if let hir::FnRetTy::Return(ref output) = decl.output {
2378             self.maybe_print_comment(output.span.lo())
2379         }
2380     }
2381
2382     pub fn print_ty_fn(
2383         &mut self,
2384         abi: Abi,
2385         unsafety: hir::Unsafety,
2386         decl: &hir::FnDecl<'_>,
2387         name: Option<Symbol>,
2388         generic_params: &[hir::GenericParam<'_>],
2389         arg_names: &[Ident],
2390     ) {
2391         self.ibox(INDENT_UNIT);
2392         if !generic_params.is_empty() {
2393             self.s.word("for");
2394             self.print_generic_params(generic_params);
2395         }
2396         let generics = hir::Generics {
2397             params: &[],
2398             where_clause: hir::WhereClause { predicates: &[], span: rustc_span::DUMMY_SP },
2399             span: rustc_span::DUMMY_SP,
2400         };
2401         self.print_fn(
2402             decl,
2403             hir::FnHeader {
2404                 unsafety,
2405                 abi,
2406                 constness: hir::Constness::NotConst,
2407                 asyncness: hir::IsAsync::NotAsync,
2408             },
2409             name,
2410             &generics,
2411             &Spanned { span: rustc_span::DUMMY_SP, node: hir::VisibilityKind::Inherited },
2412             arg_names,
2413             None,
2414         );
2415         self.end();
2416     }
2417
2418     pub fn maybe_print_trailing_comment(
2419         &mut self,
2420         span: rustc_span::Span,
2421         next_pos: Option<BytePos>,
2422     ) {
2423         if let Some(cmnts) = self.comments() {
2424             if let Some(cmnt) = cmnts.trailing_comment(span, next_pos) {
2425                 self.print_comment(&cmnt);
2426             }
2427         }
2428     }
2429
2430     pub fn print_remaining_comments(&mut self) {
2431         // If there aren't any remaining comments, then we need to manually
2432         // make sure there is a line break at the end.
2433         if self.next_comment().is_none() {
2434             self.s.hardbreak();
2435         }
2436         while let Some(ref cmnt) = self.next_comment() {
2437             self.print_comment(cmnt)
2438         }
2439     }
2440
2441     pub fn print_fn_header_info(&mut self, header: hir::FnHeader, vis: &hir::Visibility<'_>) {
2442         self.s.word(visibility_qualified(vis, ""));
2443
2444         match header.constness {
2445             hir::Constness::NotConst => {}
2446             hir::Constness::Const => self.word_nbsp("const"),
2447         }
2448
2449         match header.asyncness {
2450             hir::IsAsync::NotAsync => {}
2451             hir::IsAsync::Async => self.word_nbsp("async"),
2452         }
2453
2454         self.print_unsafety(header.unsafety);
2455
2456         if header.abi != Abi::Rust {
2457             self.word_nbsp("extern");
2458             self.word_nbsp(header.abi.to_string());
2459         }
2460
2461         self.s.word("fn")
2462     }
2463
2464     pub fn print_unsafety(&mut self, s: hir::Unsafety) {
2465         match s {
2466             hir::Unsafety::Normal => {}
2467             hir::Unsafety::Unsafe => self.word_nbsp("unsafe"),
2468         }
2469     }
2470
2471     pub fn print_is_auto(&mut self, s: hir::IsAuto) {
2472         match s {
2473             hir::IsAuto::Yes => self.word_nbsp("auto"),
2474             hir::IsAuto::No => {}
2475         }
2476     }
2477 }
2478
2479 /// Does this expression require a semicolon to be treated
2480 /// as a statement? The negation of this: 'can this expression
2481 /// be used as a statement without a semicolon' -- is used
2482 /// as an early-bail-out in the parser so that, for instance,
2483 ///     if true {...} else {...}
2484 ///      |x| 5
2485 /// isn't parsed as (if true {...} else {...} | x) | 5
2486 //
2487 // Duplicated from `parse::classify`, but adapted for the HIR.
2488 fn expr_requires_semi_to_be_stmt(e: &hir::Expr<'_>) -> bool {
2489     !matches!(
2490         e.kind,
2491         hir::ExprKind::If(..)
2492             | hir::ExprKind::Match(..)
2493             | hir::ExprKind::Block(..)
2494             | hir::ExprKind::Loop(..)
2495     )
2496 }
2497
2498 /// This statement requires a semicolon after it.
2499 /// note that in one case (stmt_semi), we've already
2500 /// seen the semicolon, and thus don't need another.
2501 fn stmt_ends_with_semi(stmt: &hir::StmtKind<'_>) -> bool {
2502     match *stmt {
2503         hir::StmtKind::Local(_) => true,
2504         hir::StmtKind::Item(_) => false,
2505         hir::StmtKind::Expr(ref e) => expr_requires_semi_to_be_stmt(&e),
2506         hir::StmtKind::Semi(..) => false,
2507     }
2508 }
2509
2510 fn bin_op_to_assoc_op(op: hir::BinOpKind) -> AssocOp {
2511     use crate::hir::BinOpKind::*;
2512     match op {
2513         Add => AssocOp::Add,
2514         Sub => AssocOp::Subtract,
2515         Mul => AssocOp::Multiply,
2516         Div => AssocOp::Divide,
2517         Rem => AssocOp::Modulus,
2518
2519         And => AssocOp::LAnd,
2520         Or => AssocOp::LOr,
2521
2522         BitXor => AssocOp::BitXor,
2523         BitAnd => AssocOp::BitAnd,
2524         BitOr => AssocOp::BitOr,
2525         Shl => AssocOp::ShiftLeft,
2526         Shr => AssocOp::ShiftRight,
2527
2528         Eq => AssocOp::Equal,
2529         Lt => AssocOp::Less,
2530         Le => AssocOp::LessEqual,
2531         Ne => AssocOp::NotEqual,
2532         Ge => AssocOp::GreaterEqual,
2533         Gt => AssocOp::Greater,
2534     }
2535 }
2536
2537 /// Expressions that syntactically contain an "exterior" struct literal, i.e., not surrounded by any
2538 /// parens or other delimiters, e.g., `X { y: 1 }`, `X { y: 1 }.method()`, `foo == X { y: 1 }` and
2539 /// `X { y: 1 } == foo` all do, but `(X { y: 1 }) == foo` does not.
2540 fn contains_exterior_struct_lit(value: &hir::Expr<'_>) -> bool {
2541     match value.kind {
2542         hir::ExprKind::Struct(..) => true,
2543
2544         hir::ExprKind::Assign(ref lhs, ref rhs, _)
2545         | hir::ExprKind::AssignOp(_, ref lhs, ref rhs)
2546         | hir::ExprKind::Binary(_, ref lhs, ref rhs) => {
2547             // `X { y: 1 } + X { y: 2 }`
2548             contains_exterior_struct_lit(&lhs) || contains_exterior_struct_lit(&rhs)
2549         }
2550         hir::ExprKind::Unary(_, ref x)
2551         | hir::ExprKind::Cast(ref x, _)
2552         | hir::ExprKind::Type(ref x, _)
2553         | hir::ExprKind::Field(ref x, _)
2554         | hir::ExprKind::Index(ref x, _) => {
2555             // `&X { y: 1 }, X { y: 1 }.y`
2556             contains_exterior_struct_lit(&x)
2557         }
2558
2559         hir::ExprKind::MethodCall(.., ref exprs, _) => {
2560             // `X { y: 1 }.bar(...)`
2561             contains_exterior_struct_lit(&exprs[0])
2562         }
2563
2564         _ => false,
2565     }
2566 }