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