src/librustdoc/html/format.rs

   1 //! HTML formatting module
   2 //!
   3 //! This module contains a large number of `fmt::Display` implementations for
   4 //! various types in `rustdoc::clean`. These implementations all currently
   5 //! assume that HTML output is desired, although it may be possible to redesign
   6 //! them in the future to instead emit any format desired.
   7
   8 use std::borrow::Cow;
   9 use std::cell::Cell;
  10 use std::fmt;
  11 use std::iter;
  12
  13 use rustc_attr::{ConstStability, StabilityLevel};
  14 use rustc_data_structures::captures::Captures;
  15 use rustc_data_structures::fx::FxHashSet;
  16 use rustc_hir as hir;
  17 use rustc_hir::def::DefKind;
  18 use rustc_hir::def_id::DefId;
  19 use rustc_middle::ty;
  20 use rustc_middle::ty::DefIdTree;
  21 use rustc_middle::ty::TyCtxt;
  22 use rustc_span::symbol::kw;
  23 use rustc_span::{sym, Symbol};
  24 use rustc_target::spec::abi::Abi;
  25
  26 use crate::clean::{
  27     self, types::ExternalLocation, utils::find_nearest_parent_module, ExternalCrate, ItemId,
  28     PrimitiveType,
  29 };
  30 use crate::formats::item_type::ItemType;
  31 use crate::html::escape::Escape;
  32 use crate::html::render::Context;
  33
  34 use super::url_parts_builder::estimate_item_path_byte_length;
  35 use super::url_parts_builder::UrlPartsBuilder;
  36
  37 pub(crate) trait Print {
  38     fn print(self, buffer: &mut Buffer);
  39 }
  40
  41 impl<F> Print for F
  42 where
  43     F: FnOnce(&mut Buffer),
  44 {
  45     fn print(self, buffer: &mut Buffer) {
  46         (self)(buffer)
  47     }
  48 }
  49
  50 impl Print for String {
  51     fn print(self, buffer: &mut Buffer) {
  52         buffer.write_str(&self);
  53     }
  54 }
  55
  56 impl Print for &'_ str {
  57     fn print(self, buffer: &mut Buffer) {
  58         buffer.write_str(self);
  59     }
  60 }
  61
  62 #[derive(Debug, Clone)]
  63 pub(crate) struct Buffer {
  64     for_html: bool,
  65     buffer: String,
  66 }
  67
  68 impl core::fmt::Write for Buffer {
  69     #[inline]
  70     fn write_str(&mut self, s: &str) -> fmt::Result {
  71         self.buffer.write_str(s)
  72     }
  73
  74     #[inline]
  75     fn write_char(&mut self, c: char) -> fmt::Result {
  76         self.buffer.write_char(c)
  77     }
  78
  79     #[inline]
  80     fn write_fmt(&mut self, args: fmt::Arguments<'_>) -> fmt::Result {
  81         self.buffer.write_fmt(args)
  82     }
  83 }
  84
  85 impl Buffer {
  86     pub(crate) fn empty_from(v: &Buffer) -> Buffer {
  87         Buffer { for_html: v.for_html, buffer: String::new() }
  88     }
  89
  90     pub(crate) fn html() -> Buffer {
  91         Buffer { for_html: true, buffer: String::new() }
  92     }
  93
  94     pub(crate) fn new() -> Buffer {
  95         Buffer { for_html: false, buffer: String::new() }
  96     }
  97
  98     pub(crate) fn is_empty(&self) -> bool {
  99         self.buffer.is_empty()
 100     }
 101
 102     pub(crate) fn into_inner(self) -> String {
 103         self.buffer
 104     }
 105
 106     pub(crate) fn insert_str(&mut self, idx: usize, s: &str) {
 107         self.buffer.insert_str(idx, s);
 108     }
 109
 110     pub(crate) fn push_str(&mut self, s: &str) {
 111         self.buffer.push_str(s);
 112     }
 113
 114     pub(crate) fn push_buffer(&mut self, other: Buffer) {
 115         self.buffer.push_str(&other.buffer);
 116     }
 117
 118     // Intended for consumption by write! and writeln! (std::fmt) but without
 119     // the fmt::Result return type imposed by fmt::Write (and avoiding the trait
 120     // import).
 121     pub(crate) fn write_str(&mut self, s: &str) {
 122         self.buffer.push_str(s);
 123     }
 124
 125     // Intended for consumption by write! and writeln! (std::fmt) but without
 126     // the fmt::Result return type imposed by fmt::Write (and avoiding the trait
 127     // import).
 128     pub(crate) fn write_fmt(&mut self, v: fmt::Arguments<'_>) {
 129         use fmt::Write;
 130         self.buffer.write_fmt(v).unwrap();
 131     }
 132
 133     pub(crate) fn to_display<T: Print>(mut self, t: T) -> String {
 134         t.print(&mut self);
 135         self.into_inner()
 136     }
 137
 138     pub(crate) fn is_for_html(&self) -> bool {
 139         self.for_html
 140     }
 141
 142     pub(crate) fn reserve(&mut self, additional: usize) {
 143         self.buffer.reserve(additional)
 144     }
 145 }
 146
 147 fn comma_sep<T: fmt::Display>(
 148     items: impl Iterator<Item = T>,
 149     space_after_comma: bool,
 150 ) -> impl fmt::Display {
 151     display_fn(move |f| {
 152         for (i, item) in items.enumerate() {
 153             if i != 0 {
 154                 write!(f, ",{}", if space_after_comma { " " } else { "" })?;
 155             }
 156             fmt::Display::fmt(&item, f)?;
 157         }
 158         Ok(())
 159     })
 160 }
 161
 162 pub(crate) fn print_generic_bounds<'a, 'tcx: 'a>(
 163     bounds: &'a [clean::GenericBound],
 164     cx: &'a Context<'tcx>,
 165 ) -> impl fmt::Display + 'a + Captures<'tcx> {
 166     display_fn(move |f| {
 167         let mut bounds_dup = FxHashSet::default();
 168
 169         for (i, bound) in bounds.iter().filter(|b| bounds_dup.insert(b.clone())).enumerate() {
 170             if i > 0 {
 171                 f.write_str(" + ")?;
 172             }
 173             fmt::Display::fmt(&bound.print(cx), f)?;
 174         }
 175         Ok(())
 176     })
 177 }
 178
 179 impl clean::GenericParamDef {
 180     pub(crate) fn print<'a, 'tcx: 'a>(
 181         &'a self,
 182         cx: &'a Context<'tcx>,
 183     ) -> impl fmt::Display + 'a + Captures<'tcx> {
 184         display_fn(move |f| match &self.kind {
 185             clean::GenericParamDefKind::Lifetime { outlives } => {
 186                 write!(f, "{}", self.name)?;
 187
 188                 if !outlives.is_empty() {
 189                     f.write_str(": ")?;
 190                     for (i, lt) in outlives.iter().enumerate() {
 191                         if i != 0 {
 192                             f.write_str(" + ")?;
 193                         }
 194                         write!(f, "{}", lt.print())?;
 195                     }
 196                 }
 197
 198                 Ok(())
 199             }
 200             clean::GenericParamDefKind::Type { bounds, default, .. } => {
 201                 f.write_str(self.name.as_str())?;
 202
 203                 if !bounds.is_empty() {
 204                     if f.alternate() {
 205                         write!(f, ": {:#}", print_generic_bounds(bounds, cx))?;
 206                     } else {
 207                         write!(f, ":&nbsp;{}", print_generic_bounds(bounds, cx))?;
 208                     }
 209                 }
 210
 211                 if let Some(ref ty) = default {
 212                     if f.alternate() {
 213                         write!(f, " = {:#}", ty.print(cx))?;
 214                     } else {
 215                         write!(f, "&nbsp;=&nbsp;{}", ty.print(cx))?;
 216                     }
 217                 }
 218
 219                 Ok(())
 220             }
 221             clean::GenericParamDefKind::Const { ty, default, .. } => {
 222                 if f.alternate() {
 223                     write!(f, "const {}: {:#}", self.name, ty.print(cx))?;
 224                 } else {
 225                     write!(f, "const {}:&nbsp;{}", self.name, ty.print(cx))?;
 226                 }
 227
 228                 if let Some(default) = default {
 229                     if f.alternate() {
 230                         write!(f, " = {:#}", default)?;
 231                     } else {
 232                         write!(f, "&nbsp;=&nbsp;{}", default)?;
 233                     }
 234                 }
 235
 236                 Ok(())
 237             }
 238         })
 239     }
 240 }
 241
 242 impl clean::Generics {
 243     pub(crate) fn print<'a, 'tcx: 'a>(
 244         &'a self,
 245         cx: &'a Context<'tcx>,
 246     ) -> impl fmt::Display + 'a + Captures<'tcx> {
 247         display_fn(move |f| {
 248             let mut real_params =
 249                 self.params.iter().filter(|p| !p.is_synthetic_type_param()).peekable();
 250             if real_params.peek().is_none() {
 251                 return Ok(());
 252             }
 253
 254             if f.alternate() {
 255                 write!(f, "<{:#}>", comma_sep(real_params.map(|g| g.print(cx)), true))
 256             } else {
 257                 write!(f, "&lt;{}&gt;", comma_sep(real_params.map(|g| g.print(cx)), true))
 258             }
 259         })
 260     }
 261 }
 262
 263 /// * The Generics from which to emit a where-clause.
 264 /// * The number of spaces to indent each line with.
 265 /// * Whether the where-clause needs to add a comma and newline after the last bound.
 266 pub(crate) fn print_where_clause<'a, 'tcx: 'a>(
 267     gens: &'a clean::Generics,
 268     cx: &'a Context<'tcx>,
 269     indent: usize,
 270     end_newline: bool,
 271 ) -> impl fmt::Display + 'a + Captures<'tcx> {
 272     use fmt::Write;
 273
 274     display_fn(move |f| {
 275         let mut where_predicates = gens.where_predicates.iter().filter(|pred| {
 276             !matches!(pred, clean::WherePredicate::BoundPredicate { bounds, .. } if bounds.is_empty())
 277         }).map(|pred| {
 278             display_fn(move |f| {
 279                 if f.alternate() {
 280                     f.write_str(" ")?;
 281                 } else {
 282                     f.write_str("<br>")?;
 283                 }
 284
 285                 match pred {
 286                     clean::WherePredicate::BoundPredicate { ty, bounds, bound_params } => {
 287                         let ty_cx = ty.print(cx);
 288                         let generic_bounds = print_generic_bounds(bounds, cx);
 289
 290                         if bound_params.is_empty() {
 291                             if f.alternate() {
 292                                 write!(f, "{ty_cx:#}: {generic_bounds:#}")
 293                             } else {
 294                                 write!(f, "{ty_cx}: {generic_bounds}")
 295                             }
 296                         } else {
 297                             if f.alternate() {
 298                                 write!(
 299                                     f,
 300                                     "for<{:#}> {ty_cx:#}: {generic_bounds:#}",
 301                                     comma_sep(bound_params.iter().map(|lt| lt.print()), true)
 302                                 )
 303                             } else {
 304                                 write!(
 305                                     f,
 306                                     "for&lt;{}&gt; {ty_cx}: {generic_bounds}",
 307                                     comma_sep(bound_params.iter().map(|lt| lt.print()), true)
 308                                 )
 309                             }
 310                         }
 311                     }
 312                     clean::WherePredicate::RegionPredicate { lifetime, bounds } => {
 313                         let mut bounds_display = String::new();
 314                         for bound in bounds.iter().map(|b| b.print(cx)) {
 315                             write!(bounds_display, "{bound} + ")?;
 316                         }
 317                         bounds_display.truncate(bounds_display.len() - " + ".len());
 318                         write!(f, "{}: {bounds_display}", lifetime.print())
 319                     }
 320                     clean::WherePredicate::EqPredicate { lhs, rhs } => {
 321                         if f.alternate() {
 322                             write!(f, "{:#} == {:#}", lhs.print(cx), rhs.print(cx))
 323                         } else {
 324                             write!(f, "{} == {}", lhs.print(cx), rhs.print(cx))
 325                         }
 326                     }
 327                 }
 328             })
 329         }).peekable();
 330
 331         if where_predicates.peek().is_none() {
 332             return Ok(());
 333         }
 334
 335         let where_preds = comma_sep(where_predicates, false);
 336         let clause = if f.alternate() {
 337             if end_newline {
 338                 // add a space so stripping <br> tags and breaking spaces still renders properly
 339                 format!(" where{where_preds}, ")
 340             } else {
 341                 format!(" where{where_preds}")
 342             }
 343         } else {
 344             let mut br_with_padding = String::with_capacity(6 * indent + 28);
 345             br_with_padding.push_str("<br>");
 346             for _ in 0..indent + 4 {
 347                 br_with_padding.push_str("&nbsp;");
 348             }
 349             let where_preds = where_preds.to_string().replace("<br>", &br_with_padding);
 350
 351             if end_newline {
 352                 let mut clause = "&nbsp;".repeat(indent.saturating_sub(1));
 353                 // add a space so stripping <br> tags and breaking spaces still renders properly
 354                 write!(
 355                     clause,
 356                     " <span class=\"where fmt-newline\">where{where_preds},&nbsp;</span>"
 357                 )?;
 358                 clause
 359             } else {
 360                 // insert a <br> tag after a single space but before multiple spaces at the start
 361                 if indent == 0 {
 362                     format!(" <br><span class=\"where\">where{where_preds}</span>")
 363                 } else {
 364                     let mut clause = br_with_padding;
 365                     clause.truncate(clause.len() - 5 * "&nbsp;".len());
 366                     write!(clause, " <span class=\"where\">where{where_preds}</span>")?;
 367                     clause
 368                 }
 369             }
 370         };
 371         write!(f, "{clause}")
 372     })
 373 }
 374
 375 impl clean::Lifetime {
 376     pub(crate) fn print(&self) -> impl fmt::Display + '_ {
 377         self.0.as_str()
 378     }
 379 }
 380
 381 impl clean::Constant {
 382     pub(crate) fn print(&self, tcx: TyCtxt<'_>) -> impl fmt::Display + '_ {
 383         let expr = self.expr(tcx);
 384         display_fn(
 385             move |f| {
 386                 if f.alternate() { f.write_str(&expr) } else { write!(f, "{}", Escape(&expr)) }
 387             },
 388         )
 389     }
 390 }
 391
 392 impl clean::PolyTrait {
 393     fn print<'a, 'tcx: 'a>(
 394         &'a self,
 395         cx: &'a Context<'tcx>,
 396     ) -> impl fmt::Display + 'a + Captures<'tcx> {
 397         display_fn(move |f| {
 398             if !self.generic_params.is_empty() {
 399                 if f.alternate() {
 400                     write!(
 401                         f,
 402                         "for<{:#}> ",
 403                         comma_sep(self.generic_params.iter().map(|g| g.print(cx)), true)
 404                     )?;
 405                 } else {
 406                     write!(
 407                         f,
 408                         "for&lt;{}&gt; ",
 409                         comma_sep(self.generic_params.iter().map(|g| g.print(cx)), true)
 410                     )?;
 411                 }
 412             }
 413             if f.alternate() {
 414                 write!(f, "{:#}", self.trait_.print(cx))
 415             } else {
 416                 write!(f, "{}", self.trait_.print(cx))
 417             }
 418         })
 419     }
 420 }
 421
 422 impl clean::GenericBound {
 423     pub(crate) fn print<'a, 'tcx: 'a>(
 424         &'a self,
 425         cx: &'a Context<'tcx>,
 426     ) -> impl fmt::Display + 'a + Captures<'tcx> {
 427         display_fn(move |f| match self {
 428             clean::GenericBound::Outlives(lt) => write!(f, "{}", lt.print()),
 429             clean::GenericBound::TraitBound(ty, modifier) => {
 430                 let modifier_str = match modifier {
 431                     hir::TraitBoundModifier::None => "",
 432                     hir::TraitBoundModifier::Maybe => "?",
 433                     // ~const is experimental; do not display those bounds in rustdoc
 434                     hir::TraitBoundModifier::MaybeConst => "",
 435                 };
 436                 if f.alternate() {
 437                     write!(f, "{}{:#}", modifier_str, ty.print(cx))
 438                 } else {
 439                     write!(f, "{}{}", modifier_str, ty.print(cx))
 440                 }
 441             }
 442         })
 443     }
 444 }
 445
 446 impl clean::GenericArgs {
 447     fn print<'a, 'tcx: 'a>(
 448         &'a self,
 449         cx: &'a Context<'tcx>,
 450     ) -> impl fmt::Display + 'a + Captures<'tcx> {
 451         display_fn(move |f| {
 452             match self {
 453                 clean::GenericArgs::AngleBracketed { args, bindings } => {
 454                     if !args.is_empty() || !bindings.is_empty() {
 455                         if f.alternate() {
 456                             f.write_str("<")?;
 457                         } else {
 458                             f.write_str("&lt;")?;
 459                         }
 460                         let mut comma = false;
 461                         for arg in args.iter() {
 462                             if comma {
 463                                 f.write_str(", ")?;
 464                             }
 465                             comma = true;
 466                             if f.alternate() {
 467                                 write!(f, "{:#}", arg.print(cx))?;
 468                             } else {
 469                                 write!(f, "{}", arg.print(cx))?;
 470                             }
 471                         }
 472                         for binding in bindings.iter() {
 473                             if comma {
 474                                 f.write_str(", ")?;
 475                             }
 476                             comma = true;
 477                             if f.alternate() {
 478                                 write!(f, "{:#}", binding.print(cx))?;
 479                             } else {
 480                                 write!(f, "{}", binding.print(cx))?;
 481                             }
 482                         }
 483                         if f.alternate() {
 484                             f.write_str(">")?;
 485                         } else {
 486                             f.write_str("&gt;")?;
 487                         }
 488                     }
 489                 }
 490                 clean::GenericArgs::Parenthesized { inputs, output } => {
 491                     f.write_str("(")?;
 492                     let mut comma = false;
 493                     for ty in inputs.iter() {
 494                         if comma {
 495                             f.write_str(", ")?;
 496                         }
 497                         comma = true;
 498                         if f.alternate() {
 499                             write!(f, "{:#}", ty.print(cx))?;
 500                         } else {
 501                             write!(f, "{}", ty.print(cx))?;
 502                         }
 503                     }
 504                     f.write_str(")")?;
 505                     if let Some(ref ty) = *output {
 506                         if f.alternate() {
 507                             write!(f, " -> {:#}", ty.print(cx))?;
 508                         } else {
 509                             write!(f, " -&gt; {}", ty.print(cx))?;
 510                         }
 511                     }
 512                 }
 513             }
 514             Ok(())
 515         })
 516     }
 517 }
 518
 519 // Possible errors when computing href link source for a `DefId`
 520 pub(crate) enum HrefError {
 521     /// This item is known to rustdoc, but from a crate that does not have documentation generated.
 522     ///
 523     /// This can only happen for non-local items.
 524     ///
 525     /// # Example
 526     ///
 527     /// Crate `a` defines a public trait and crate `b` – the target crate that depends on `a` –
 528     /// implements it for a local type.
 529     /// We document `b` but **not** `a` (we only _build_ the latter – with `rustc`):
 530     ///
 531     /// ```sh
 532     /// rustc a.rs --crate-type=lib
 533     /// rustdoc b.rs --crate-type=lib --extern=a=liba.rlib
 534     /// ```
 535     ///
 536     /// Now, the associated items in the trait impl want to link to the corresponding item in the
 537     /// trait declaration (see `html::render::assoc_href_attr`) but it's not available since their
 538     /// *documentation (was) not built*.
 539     DocumentationNotBuilt,
 540     /// This can only happen for non-local items when `--document-private-items` is not passed.
 541     Private,
 542     // Not in external cache, href link should be in same page
 543     NotInExternalCache,
 544 }
 545
 546 // Panics if `syms` is empty.
 547 pub(crate) fn join_with_double_colon(syms: &[Symbol]) -> String {
 548     let mut s = String::with_capacity(estimate_item_path_byte_length(syms.len()));
 549     s.push_str(syms[0].as_str());
 550     for sym in &syms[1..] {
 551         s.push_str("::");
 552         s.push_str(sym.as_str());
 553     }
 554     s
 555 }
 556
 557 pub(crate) fn href_with_root_path(
 558     did: DefId,
 559     cx: &Context<'_>,
 560     root_path: Option<&str>,
 561 ) -> Result<(String, ItemType, Vec<Symbol>), HrefError> {
 562     let tcx = cx.tcx();
 563     let def_kind = tcx.def_kind(did);
 564     let did = match def_kind {
 565         DefKind::AssocTy | DefKind::AssocFn | DefKind::AssocConst | DefKind::Variant => {
 566             // documented on their parent's page
 567             tcx.parent(did)
 568         }
 569         _ => did,
 570     };
 571     let cache = cx.cache();
 572     let relative_to = &cx.current;
 573     fn to_module_fqp(shortty: ItemType, fqp: &[Symbol]) -> &[Symbol] {
 574         if shortty == ItemType::Module { fqp } else { &fqp[..fqp.len() - 1] }
 575     }
 576
 577     if !did.is_local()
 578         && !cache.access_levels.is_public(did)
 579         && !cache.document_private
 580         && !cache.primitive_locations.values().any(|&id| id == did)
 581     {
 582         return Err(HrefError::Private);
 583     }
 584
 585     let mut is_remote = false;
 586     let (fqp, shortty, mut url_parts) = match cache.paths.get(&did) {
 587         Some(&(ref fqp, shortty)) => (fqp, shortty, {
 588             let module_fqp = to_module_fqp(shortty, fqp.as_slice());
 589             debug!(?fqp, ?shortty, ?module_fqp);
 590             href_relative_parts(module_fqp, relative_to).collect()
 591         }),
 592         None => {
 593             if let Some(&(ref fqp, shortty)) = cache.external_paths.get(&did) {
 594                 let module_fqp = to_module_fqp(shortty, fqp);
 595                 (
 596                     fqp,
 597                     shortty,
 598                     match cache.extern_locations[&did.krate] {
 599                         ExternalLocation::Remote(ref s) => {
 600                             is_remote = true;
 601                             let s = s.trim_end_matches('/');
 602                             let mut builder = UrlPartsBuilder::singleton(s);
 603                             builder.extend(module_fqp.iter().copied());
 604                             builder
 605                         }
 606                         ExternalLocation::Local => {
 607                             href_relative_parts(module_fqp, relative_to).collect()
 608                         }
 609                         ExternalLocation::Unknown => return Err(HrefError::DocumentationNotBuilt),
 610                     },
 611                 )
 612             } else {
 613                 return Err(HrefError::NotInExternalCache);
 614             }
 615         }
 616     };
 617     if !is_remote {
 618         if let Some(root_path) = root_path {
 619             let root = root_path.trim_end_matches('/');
 620             url_parts.push_front(root);
 621         }
 622     }
 623     debug!(?url_parts);
 624     match shortty {
 625         ItemType::Module => {
 626             url_parts.push("index.html");
 627         }
 628         _ => {
 629             let prefix = shortty.as_str();
 630             let last = fqp.last().unwrap();
 631             url_parts.push_fmt(format_args!("{}.{}.html", prefix, last));
 632         }
 633     }
 634     Ok((url_parts.finish(), shortty, fqp.to_vec()))
 635 }
 636
 637 pub(crate) fn href(
 638     did: DefId,
 639     cx: &Context<'_>,
 640 ) -> Result<(String, ItemType, Vec<Symbol>), HrefError> {
 641     href_with_root_path(did, cx, None)
 642 }
 643
 644 /// Both paths should only be modules.
 645 /// This is because modules get their own directories; that is, `std::vec` and `std::vec::Vec` will
 646 /// both need `../iter/trait.Iterator.html` to get at the iterator trait.
 647 pub(crate) fn href_relative_parts<'fqp>(
 648     fqp: &'fqp [Symbol],
 649     relative_to_fqp: &[Symbol],
 650 ) -> Box<dyn Iterator<Item = Symbol> + 'fqp> {
 651     for (i, (f, r)) in fqp.iter().zip(relative_to_fqp.iter()).enumerate() {
 652         // e.g. linking to std::iter from std::vec (`dissimilar_part_count` will be 1)
 653         if f != r {
 654             let dissimilar_part_count = relative_to_fqp.len() - i;
 655             let fqp_module = &fqp[i..fqp.len()];
 656             return box iter::repeat(sym::dotdot)
 657                 .take(dissimilar_part_count)
 658                 .chain(fqp_module.iter().copied());
 659         }
 660     }
 661     // e.g. linking to std::sync::atomic from std::sync
 662     if relative_to_fqp.len() < fqp.len() {
 663         box fqp[relative_to_fqp.len()..fqp.len()].iter().copied()
 664     // e.g. linking to std::sync from std::sync::atomic
 665     } else if fqp.len() < relative_to_fqp.len() {
 666         let dissimilar_part_count = relative_to_fqp.len() - fqp.len();
 667         box iter::repeat(sym::dotdot).take(dissimilar_part_count)
 668     // linking to the same module
 669     } else {
 670         box iter::empty()
 671     }
 672 }
 673
 674 /// Used to render a [`clean::Path`].
 675 fn resolved_path<'cx>(
 676     w: &mut fmt::Formatter<'_>,
 677     did: DefId,
 678     path: &clean::Path,
 679     print_all: bool,
 680     use_absolute: bool,
 681     cx: &'cx Context<'_>,
 682 ) -> fmt::Result {
 683     let last = path.segments.last().unwrap();
 684
 685     if print_all {
 686         for seg in &path.segments[..path.segments.len() - 1] {
 687             write!(w, "{}::", if seg.name == kw::PathRoot { "" } else { seg.name.as_str() })?;
 688         }
 689     }
 690     if w.alternate() {
 691         write!(w, "{}{:#}", &last.name, last.args.print(cx))?;
 692     } else {
 693         let path = if use_absolute {
 694             if let Ok((_, _, fqp)) = href(did, cx) {
 695                 format!(
 696                     "{}::{}",
 697                     join_with_double_colon(&fqp[..fqp.len() - 1]),
 698                     anchor(did, *fqp.last().unwrap(), cx)
 699                 )
 700             } else {
 701                 last.name.to_string()
 702             }
 703         } else {
 704             anchor(did, last.name, cx).to_string()
 705         };
 706         write!(w, "{}{}", path, last.args.print(cx))?;
 707     }
 708     Ok(())
 709 }
 710
 711 fn primitive_link(
 712     f: &mut fmt::Formatter<'_>,
 713     prim: clean::PrimitiveType,
 714     name: &str,
 715     cx: &Context<'_>,
 716 ) -> fmt::Result {
 717     let m = &cx.cache();
 718     let mut needs_termination = false;
 719     if !f.alternate() {
 720         match m.primitive_locations.get(&prim) {
 721             Some(&def_id) if def_id.is_local() => {
 722                 let len = cx.current.len();
 723                 let len = if len == 0 { 0 } else { len - 1 };
 724                 write!(
 725                     f,
 726                     "<a class=\"primitive\" href=\"{}primitive.{}.html\">",
 727                     "../".repeat(len),
 728                     prim.as_sym()
 729                 )?;
 730                 needs_termination = true;
 731             }
 732             Some(&def_id) => {
 733                 let loc = match m.extern_locations[&def_id.krate] {
 734                     ExternalLocation::Remote(ref s) => {
 735                         let cname_sym = ExternalCrate { crate_num: def_id.krate }.name(cx.tcx());
 736                         let builder: UrlPartsBuilder =
 737                             [s.as_str().trim_end_matches('/'), cname_sym.as_str()]
 738                                 .into_iter()
 739                                 .collect();
 740                         Some(builder)
 741                     }
 742                     ExternalLocation::Local => {
 743                         let cname_sym = ExternalCrate { crate_num: def_id.krate }.name(cx.tcx());
 744                         Some(if cx.current.first() == Some(&cname_sym) {
 745                             iter::repeat(sym::dotdot).take(cx.current.len() - 1).collect()
 746                         } else {
 747                             iter::repeat(sym::dotdot)
 748                                 .take(cx.current.len())
 749                                 .chain(iter::once(cname_sym))
 750                                 .collect()
 751                         })
 752                     }
 753                     ExternalLocation::Unknown => None,
 754                 };
 755                 if let Some(mut loc) = loc {
 756                     loc.push_fmt(format_args!("primitive.{}.html", prim.as_sym()));
 757                     write!(f, "<a class=\"primitive\" href=\"{}\">", loc.finish())?;
 758                     needs_termination = true;
 759                 }
 760             }
 761             None => {}
 762         }
 763     }
 764     write!(f, "{}", name)?;
 765     if needs_termination {
 766         write!(f, "</a>")?;
 767     }
 768     Ok(())
 769 }
 770
 771 /// Helper to render type parameters
 772 fn tybounds<'a, 'tcx: 'a>(
 773     bounds: &'a [clean::PolyTrait],
 774     lt: &'a Option<clean::Lifetime>,
 775     cx: &'a Context<'tcx>,
 776 ) -> impl fmt::Display + 'a + Captures<'tcx> {
 777     display_fn(move |f| {
 778         for (i, bound) in bounds.iter().enumerate() {
 779             if i > 0 {
 780                 write!(f, " + ")?;
 781             }
 782
 783             fmt::Display::fmt(&bound.print(cx), f)?;
 784         }
 785
 786         if let Some(lt) = lt {
 787             write!(f, " + ")?;
 788             fmt::Display::fmt(&lt.print(), f)?;
 789         }
 790         Ok(())
 791     })
 792 }
 793
 794 pub(crate) fn anchor<'a, 'cx: 'a>(
 795     did: DefId,
 796     text: Symbol,
 797     cx: &'cx Context<'_>,
 798 ) -> impl fmt::Display + 'a {
 799     let parts = href(did, cx);
 800     display_fn(move |f| {
 801         if let Ok((url, short_ty, fqp)) = parts {
 802             write!(
 803                 f,
 804                 r#"<a class="{}" href="{}" title="{} {}">{}</a>"#,
 805                 short_ty,
 806                 url,
 807                 short_ty,
 808                 join_with_double_colon(&fqp),
 809                 text.as_str()
 810             )
 811         } else {
 812             write!(f, "{}", text)
 813         }
 814     })
 815 }
 816
 817 fn fmt_type<'cx>(
 818     t: &clean::Type,
 819     f: &mut fmt::Formatter<'_>,
 820     use_absolute: bool,
 821     cx: &'cx Context<'_>,
 822 ) -> fmt::Result {
 823     trace!("fmt_type(t = {:?})", t);
 824
 825     match *t {
 826         clean::Generic(name) => write!(f, "{}", name),
 827         clean::Type::Path { ref path } => {
 828             // Paths like `T::Output` and `Self::Output` should be rendered with all segments.
 829             let did = path.def_id();
 830             resolved_path(f, did, path, path.is_assoc_ty(), use_absolute, cx)
 831         }
 832         clean::DynTrait(ref bounds, ref lt) => {
 833             f.write_str("dyn ")?;
 834             fmt::Display::fmt(&tybounds(bounds, lt, cx), f)
 835         }
 836         clean::Infer => write!(f, "_"),
 837         clean::Primitive(clean::PrimitiveType::Never) => {
 838             primitive_link(f, PrimitiveType::Never, "!", cx)
 839         }
 840         clean::Primitive(prim) => primitive_link(f, prim, prim.as_sym().as_str(), cx),
 841         clean::BareFunction(ref decl) => {
 842             if f.alternate() {
 843                 write!(
 844                     f,
 845                     "{:#}{}{:#}fn{:#}",
 846                     decl.print_hrtb_with_space(cx),
 847                     decl.unsafety.print_with_space(),
 848                     print_abi_with_space(decl.abi),
 849                     decl.decl.print(cx),
 850                 )
 851             } else {
 852                 write!(
 853                     f,
 854                     "{}{}{}",
 855                     decl.print_hrtb_with_space(cx),
 856                     decl.unsafety.print_with_space(),
 857                     print_abi_with_space(decl.abi)
 858                 )?;
 859                 primitive_link(f, PrimitiveType::Fn, "fn", cx)?;
 860                 write!(f, "{}", decl.decl.print(cx))
 861             }
 862         }
 863         clean::Tuple(ref typs) => {
 864             match &typs[..] {
 865                 &[] => primitive_link(f, PrimitiveType::Unit, "()", cx),
 866                 &[ref one] => {
 867                     primitive_link(f, PrimitiveType::Tuple, "(", cx)?;
 868                     // Carry `f.alternate()` into this display w/o branching manually.
 869                     fmt::Display::fmt(&one.print(cx), f)?;
 870                     primitive_link(f, PrimitiveType::Tuple, ",)", cx)
 871                 }
 872                 many => {
 873                     primitive_link(f, PrimitiveType::Tuple, "(", cx)?;
 874                     for (i, item) in many.iter().enumerate() {
 875                         if i != 0 {
 876                             write!(f, ", ")?;
 877                         }
 878                         fmt::Display::fmt(&item.print(cx), f)?;
 879                     }
 880                     primitive_link(f, PrimitiveType::Tuple, ")", cx)
 881                 }
 882             }
 883         }
 884         clean::Slice(ref t) => {
 885             primitive_link(f, PrimitiveType::Slice, "[", cx)?;
 886             fmt::Display::fmt(&t.print(cx), f)?;
 887             primitive_link(f, PrimitiveType::Slice, "]", cx)
 888         }
 889         clean::Array(ref t, ref n) => {
 890             primitive_link(f, PrimitiveType::Array, "[", cx)?;
 891             fmt::Display::fmt(&t.print(cx), f)?;
 892             if f.alternate() {
 893                 primitive_link(f, PrimitiveType::Array, &format!("; {}]", n), cx)
 894             } else {
 895                 primitive_link(f, PrimitiveType::Array, &format!("; {}]", Escape(n)), cx)
 896             }
 897         }
 898         clean::RawPointer(m, ref t) => {
 899             let m = match m {
 900                 hir::Mutability::Mut => "mut",
 901                 hir::Mutability::Not => "const",
 902             };
 903
 904             if matches!(**t, clean::Generic(_)) || t.is_assoc_ty() {
 905                 let text = if f.alternate() {
 906                     format!("*{} {:#}", m, t.print(cx))
 907                 } else {
 908                     format!("*{} {}", m, t.print(cx))
 909                 };
 910                 primitive_link(f, clean::PrimitiveType::RawPointer, &text, cx)
 911             } else {
 912                 primitive_link(f, clean::PrimitiveType::RawPointer, &format!("*{} ", m), cx)?;
 913                 fmt::Display::fmt(&t.print(cx), f)
 914             }
 915         }
 916         clean::BorrowedRef { lifetime: ref l, mutability, type_: ref ty } => {
 917             let lt = match l {
 918                 Some(l) => format!("{} ", l.print()),
 919                 _ => String::new(),
 920             };
 921             let m = mutability.print_with_space();
 922             let amp = if f.alternate() { "&".to_string() } else { "&amp;".to_string() };
 923             match **ty {
 924                 clean::Slice(ref bt) => {
 925                     // `BorrowedRef{ ... Slice(T) }` is `&[T]`
 926                     match **bt {
 927                         clean::Generic(_) => {
 928                             if f.alternate() {
 929                                 primitive_link(
 930                                     f,
 931                                     PrimitiveType::Slice,
 932                                     &format!("{}{}{}[{:#}]", amp, lt, m, bt.print(cx)),
 933                                     cx,
 934                                 )
 935                             } else {
 936                                 primitive_link(
 937                                     f,
 938                                     PrimitiveType::Slice,
 939                                     &format!("{}{}{}[{}]", amp, lt, m, bt.print(cx)),
 940                                     cx,
 941                                 )
 942                             }
 943                         }
 944                         _ => {
 945                             primitive_link(
 946                                 f,
 947                                 PrimitiveType::Slice,
 948                                 &format!("{}{}{}[", amp, lt, m),
 949                                 cx,
 950                             )?;
 951                             if f.alternate() {
 952                                 write!(f, "{:#}", bt.print(cx))?;
 953                             } else {
 954                                 write!(f, "{}", bt.print(cx))?;
 955                             }
 956                             primitive_link(f, PrimitiveType::Slice, "]", cx)
 957                         }
 958                     }
 959                 }
 960                 clean::DynTrait(ref bounds, ref trait_lt)
 961                     if bounds.len() > 1 || trait_lt.is_some() =>
 962                 {
 963                     write!(f, "{}{}{}(", amp, lt, m)?;
 964                     fmt_type(ty, f, use_absolute, cx)?;
 965                     write!(f, ")")
 966                 }
 967                 clean::Generic(..) => {
 968                     primitive_link(
 969                         f,
 970                         PrimitiveType::Reference,
 971                         &format!("{}{}{}", amp, lt, m),
 972                         cx,
 973                     )?;
 974                     fmt_type(ty, f, use_absolute, cx)
 975                 }
 976                 _ => {
 977                     write!(f, "{}{}{}", amp, lt, m)?;
 978                     fmt_type(ty, f, use_absolute, cx)
 979                 }
 980             }
 981         }
 982         clean::ImplTrait(ref bounds) => {
 983             if f.alternate() {
 984                 write!(f, "impl {:#}", print_generic_bounds(bounds, cx))
 985             } else {
 986                 write!(f, "impl {}", print_generic_bounds(bounds, cx))
 987             }
 988         }
 989         clean::QPath { ref assoc, ref self_type, ref trait_, should_show_cast } => {
 990             if f.alternate() {
 991                 if should_show_cast {
 992                     write!(f, "<{:#} as {:#}>::", self_type.print(cx), trait_.print(cx))?
 993                 } else {
 994                     write!(f, "{:#}::", self_type.print(cx))?
 995                 }
 996             } else {
 997                 if should_show_cast {
 998                     write!(f, "&lt;{} as {}&gt;::", self_type.print(cx), trait_.print(cx))?
 999                 } else {
1000                     write!(f, "{}::", self_type.print(cx))?
1001                 }
1002             };
1003             // It's pretty unsightly to look at `<A as B>::C` in output, and
1004             // we've got hyperlinking on our side, so try to avoid longer
1005             // notation as much as possible by making `C` a hyperlink to trait
1006             // `B` to disambiguate.
1007             //
1008             // FIXME: this is still a lossy conversion and there should probably
1009             //        be a better way of representing this in general? Most of
1010             //        the ugliness comes from inlining across crates where
1011             //        everything comes in as a fully resolved QPath (hard to
1012             //        look at).
1013             match href(trait_.def_id(), cx) {
1014                 Ok((ref url, _, ref path)) if !f.alternate() => {
1015                     write!(
1016                         f,
1017                         "<a class=\"associatedtype\" href=\"{url}#{shortty}.{name}\" \
1018                                     title=\"type {path}::{name}\">{name}</a>{args}",
1019                         url = url,
1020                         shortty = ItemType::AssocType,
1021                         name = assoc.name,
1022                         path = join_with_double_colon(path),
1023                         args = assoc.args.print(cx),
1024                     )?;
1025                 }
1026                 _ => write!(f, "{}{:#}", assoc.name, assoc.args.print(cx))?,
1027             }
1028             Ok(())
1029         }
1030     }
1031 }
1032
1033 impl clean::Type {
1034     pub(crate) fn print<'b, 'a: 'b, 'tcx: 'a>(
1035         &'a self,
1036         cx: &'a Context<'tcx>,
1037     ) -> impl fmt::Display + 'b + Captures<'tcx> {
1038         display_fn(move |f| fmt_type(self, f, false, cx))
1039     }
1040 }
1041
1042 impl clean::Path {
1043     pub(crate) fn print<'b, 'a: 'b, 'tcx: 'a>(
1044         &'a self,
1045         cx: &'a Context<'tcx>,
1046     ) -> impl fmt::Display + 'b + Captures<'tcx> {
1047         display_fn(move |f| resolved_path(f, self.def_id(), self, false, false, cx))
1048     }
1049 }
1050
1051 impl clean::Impl {
1052     pub(crate) fn print<'a, 'tcx: 'a>(
1053         &'a self,
1054         use_absolute: bool,
1055         cx: &'a Context<'tcx>,
1056     ) -> impl fmt::Display + 'a + Captures<'tcx> {
1057         display_fn(move |f| {
1058             if f.alternate() {
1059                 write!(f, "impl{:#} ", self.generics.print(cx))?;
1060             } else {
1061                 write!(f, "impl{} ", self.generics.print(cx))?;
1062             }
1063
1064             if let Some(ref ty) = self.trait_ {
1065                 match self.polarity {
1066                     ty::ImplPolarity::Positive | ty::ImplPolarity::Reservation => {}
1067                     ty::ImplPolarity::Negative => write!(f, "!")?,
1068                 }
1069                 fmt::Display::fmt(&ty.print(cx), f)?;
1070                 write!(f, " for ")?;
1071             }
1072
1073             if let Some(ty) = self.kind.as_blanket_ty() {
1074                 fmt_type(ty, f, use_absolute, cx)?;
1075             } else {
1076                 fmt_type(&self.for_, f, use_absolute, cx)?;
1077             }
1078
1079             fmt::Display::fmt(&print_where_clause(&self.generics, cx, 0, true), f)?;
1080             Ok(())
1081         })
1082     }
1083 }
1084
1085 impl clean::Arguments {
1086     pub(crate) fn print<'a, 'tcx: 'a>(
1087         &'a self,
1088         cx: &'a Context<'tcx>,
1089     ) -> impl fmt::Display + 'a + Captures<'tcx> {
1090         display_fn(move |f| {
1091             for (i, input) in self.values.iter().enumerate() {
1092                 if !input.name.is_empty() {
1093                     write!(f, "{}: ", input.name)?;
1094                 }
1095                 if f.alternate() {
1096                     write!(f, "{:#}", input.type_.print(cx))?;
1097                 } else {
1098                     write!(f, "{}", input.type_.print(cx))?;
1099                 }
1100                 if i + 1 < self.values.len() {
1101                     write!(f, ", ")?;
1102                 }
1103             }
1104             Ok(())
1105         })
1106     }
1107 }
1108
1109 impl clean::FnRetTy {
1110     pub(crate) fn print<'a, 'tcx: 'a>(
1111         &'a self,
1112         cx: &'a Context<'tcx>,
1113     ) -> impl fmt::Display + 'a + Captures<'tcx> {
1114         display_fn(move |f| match self {
1115             clean::Return(clean::Tuple(tys)) if tys.is_empty() => Ok(()),
1116             clean::Return(ty) if f.alternate() => {
1117                 write!(f, " -> {:#}", ty.print(cx))
1118             }
1119             clean::Return(ty) => write!(f, " -&gt; {}", ty.print(cx)),
1120             clean::DefaultReturn => Ok(()),
1121         })
1122     }
1123 }
1124
1125 impl clean::BareFunctionDecl {
1126     fn print_hrtb_with_space<'a, 'tcx: 'a>(
1127         &'a self,
1128         cx: &'a Context<'tcx>,
1129     ) -> impl fmt::Display + 'a + Captures<'tcx> {
1130         display_fn(move |f| {
1131             if !self.generic_params.is_empty() {
1132                 write!(
1133                     f,
1134                     "for&lt;{}&gt; ",
1135                     comma_sep(self.generic_params.iter().map(|g| g.print(cx)), true)
1136                 )
1137             } else {
1138                 Ok(())
1139             }
1140         })
1141     }
1142 }
1143
1144 impl clean::FnDecl {
1145     pub(crate) fn print<'b, 'a: 'b, 'tcx: 'a>(
1146         &'a self,
1147         cx: &'a Context<'tcx>,
1148     ) -> impl fmt::Display + 'b + Captures<'tcx> {
1149         display_fn(move |f| {
1150             let ellipsis = if self.c_variadic { ", ..." } else { "" };
1151             if f.alternate() {
1152                 write!(
1153                     f,
1154                     "({args:#}{ellipsis}){arrow:#}",
1155                     args = self.inputs.print(cx),
1156                     ellipsis = ellipsis,
1157                     arrow = self.output.print(cx)
1158                 )
1159             } else {
1160                 write!(
1161                     f,
1162                     "({args}{ellipsis}){arrow}",
1163                     args = self.inputs.print(cx),
1164                     ellipsis = ellipsis,
1165                     arrow = self.output.print(cx)
1166                 )
1167             }
1168         })
1169     }
1170
1171     /// * `header_len`: The length of the function header and name. In other words, the number of
1172     ///   characters in the function declaration up to but not including the parentheses.
1173     ///   <br>Used to determine line-wrapping.
1174     /// * `indent`: The number of spaces to indent each successive line with, if line-wrapping is
1175     ///   necessary.
1176     /// * `asyncness`: Whether the function is async or not.
1177     pub(crate) fn full_print<'a, 'tcx: 'a>(
1178         &'a self,
1179         header_len: usize,
1180         indent: usize,
1181         asyncness: hir::IsAsync,
1182         cx: &'a Context<'tcx>,
1183     ) -> impl fmt::Display + 'a + Captures<'tcx> {
1184         display_fn(move |f| self.inner_full_print(header_len, indent, asyncness, f, cx))
1185     }
1186
1187     fn inner_full_print(
1188         &self,
1189         header_len: usize,
1190         indent: usize,
1191         asyncness: hir::IsAsync,
1192         f: &mut fmt::Formatter<'_>,
1193         cx: &Context<'_>,
1194     ) -> fmt::Result {
1195         let amp = if f.alternate() { "&" } else { "&amp;" };
1196         let mut args = Buffer::html();
1197         let mut args_plain = Buffer::new();
1198         for (i, input) in self.inputs.values.iter().enumerate() {
1199             if i == 0 {
1200                 args.push_str("<br>");
1201             }
1202
1203             if let Some(selfty) = input.to_self() {
1204                 match selfty {
1205                     clean::SelfValue => {
1206                         args.push_str("self");
1207                         args_plain.push_str("self");
1208                     }
1209                     clean::SelfBorrowed(Some(ref lt), mtbl) => {
1210                         write!(args, "{}{} {}self", amp, lt.print(), mtbl.print_with_space());
1211                         write!(args_plain, "&{} {}self", lt.print(), mtbl.print_with_space());
1212                     }
1213                     clean::SelfBorrowed(None, mtbl) => {
1214                         write!(args, "{}{}self", amp, mtbl.print_with_space());
1215                         write!(args_plain, "&{}self", mtbl.print_with_space());
1216                     }
1217                     clean::SelfExplicit(ref typ) => {
1218                         if f.alternate() {
1219                             write!(args, "self: {:#}", typ.print(cx));
1220                         } else {
1221                             write!(args, "self: {}", typ.print(cx));
1222                         }
1223                         write!(args_plain, "self: {:#}", typ.print(cx));
1224                     }
1225                 }
1226             } else {
1227                 if i > 0 {
1228                     args.push_str(" <br>");
1229                     args_plain.push_str(" ");
1230                 }
1231                 if input.is_const {
1232                     args.push_str("const ");
1233                     args_plain.push_str("const ");
1234                 }
1235                 if !input.name.is_empty() {
1236                     write!(args, "{}: ", input.name);
1237                     write!(args_plain, "{}: ", input.name);
1238                 }
1239
1240                 if f.alternate() {
1241                     write!(args, "{:#}", input.type_.print(cx));
1242                 } else {
1243                     write!(args, "{}", input.type_.print(cx));
1244                 }
1245                 write!(args_plain, "{:#}", input.type_.print(cx));
1246             }
1247             if i + 1 < self.inputs.values.len() {
1248                 args.push_str(",");
1249                 args_plain.push_str(",");
1250             }
1251         }
1252
1253         let mut args_plain = format!("({})", args_plain.into_inner());
1254         let mut args = args.into_inner();
1255
1256         if self.c_variadic {
1257             args.push_str(",<br> ...");
1258             args_plain.push_str(", ...");
1259         }
1260
1261         let arrow_plain;
1262         let arrow = if let hir::IsAsync::Async = asyncness {
1263             let output = self.sugared_async_return_type();
1264             arrow_plain = format!("{:#}", output.print(cx));
1265             if f.alternate() { arrow_plain.clone() } else { format!("{}", output.print(cx)) }
1266         } else {
1267             arrow_plain = format!("{:#}", self.output.print(cx));
1268             if f.alternate() { arrow_plain.clone() } else { format!("{}", self.output.print(cx)) }
1269         };
1270
1271         let declaration_len = header_len + args_plain.len() + arrow_plain.len();
1272         let output = if declaration_len > 80 {
1273             let full_pad = format!("<br>{}", "&nbsp;".repeat(indent + 4));
1274             let close_pad = format!("<br>{}", "&nbsp;".repeat(indent));
1275             format!(
1276                 "({args}{close}){arrow}",
1277                 args = args.replace("<br>", &full_pad),
1278                 close = close_pad,
1279                 arrow = arrow
1280             )
1281         } else {
1282             format!("({args}){arrow}", args = args.replace("<br>", ""), arrow = arrow)
1283         };
1284
1285         if f.alternate() {
1286             write!(f, "{}", output.replace("<br>", "\n"))
1287         } else {
1288             write!(f, "{}", output)
1289         }
1290     }
1291 }
1292
1293 impl clean::Visibility {
1294     pub(crate) fn print_with_space<'a, 'tcx: 'a>(
1295         self,
1296         item_did: ItemId,
1297         cx: &'a Context<'tcx>,
1298     ) -> impl fmt::Display + 'a + Captures<'tcx> {
1299         use std::fmt::Write as _;
1300
1301         let to_print: Cow<'static, str> = match self {
1302             clean::Public => "pub ".into(),
1303             clean::Inherited => "".into(),
1304             clean::Visibility::Restricted(vis_did) => {
1305                 // FIXME(camelid): This may not work correctly if `item_did` is a module.
1306                 //                 However, rustdoc currently never displays a module's
1307                 //                 visibility, so it shouldn't matter.
1308                 let parent_module = find_nearest_parent_module(cx.tcx(), item_did.expect_def_id());
1309
1310                 if vis_did.is_crate_root() {
1311                     "pub(crate) ".into()
1312                 } else if parent_module == Some(vis_did) {
1313                     // `pub(in foo)` where `foo` is the parent module
1314                     // is the same as no visibility modifier
1315                     "".into()
1316                 } else if parent_module
1317                     .and_then(|parent| find_nearest_parent_module(cx.tcx(), parent))
1318                     == Some(vis_did)
1319                 {
1320                     "pub(super) ".into()
1321                 } else {
1322                     let path = cx.tcx().def_path(vis_did);
1323                     debug!("path={:?}", path);
1324                     // modified from `resolved_path()` to work with `DefPathData`
1325                     let last_name = path.data.last().unwrap().data.get_opt_name().unwrap();
1326                     let anchor = anchor(vis_did, last_name, cx).to_string();
1327
1328                     let mut s = "pub(in ".to_owned();
1329                     for seg in &path.data[..path.data.len() - 1] {
1330                         let _ = write!(s, "{}::", seg.data.get_opt_name().unwrap());
1331                     }
1332                     let _ = write!(s, "{}) ", anchor);
1333                     s.into()
1334                 }
1335             }
1336         };
1337         display_fn(move |f| write!(f, "{}", to_print))
1338     }
1339
1340     /// This function is the same as print_with_space, except that it renders no links.
1341     /// It's used for macros' rendered source view, which is syntax highlighted and cannot have
1342     /// any HTML in it.
1343     pub(crate) fn to_src_with_space<'a, 'tcx: 'a>(
1344         self,
1345         tcx: TyCtxt<'tcx>,
1346         item_did: DefId,
1347     ) -> impl fmt::Display + 'a + Captures<'tcx> {
1348         let to_print = match self {
1349             clean::Public => "pub ".to_owned(),
1350             clean::Inherited => String::new(),
1351             clean::Visibility::Restricted(vis_did) => {
1352                 // FIXME(camelid): This may not work correctly if `item_did` is a module.
1353                 //                 However, rustdoc currently never displays a module's
1354                 //                 visibility, so it shouldn't matter.
1355                 let parent_module = find_nearest_parent_module(tcx, item_did);
1356
1357                 if vis_did.is_crate_root() {
1358                     "pub(crate) ".to_owned()
1359                 } else if parent_module == Some(vis_did) {
1360                     // `pub(in foo)` where `foo` is the parent module
1361                     // is the same as no visibility modifier
1362                     String::new()
1363                 } else if parent_module.and_then(|parent| find_nearest_parent_module(tcx, parent))
1364                     == Some(vis_did)
1365                 {
1366                     "pub(super) ".to_owned()
1367                 } else {
1368                     format!("pub(in {}) ", tcx.def_path_str(vis_did))
1369                 }
1370             }
1371         };
1372         display_fn(move |f| f.write_str(&to_print))
1373     }
1374 }
1375
1376 pub(crate) trait PrintWithSpace {
1377     fn print_with_space(&self) -> &str;
1378 }
1379
1380 impl PrintWithSpace for hir::Unsafety {
1381     fn print_with_space(&self) -> &str {
1382         match self {
1383             hir::Unsafety::Unsafe => "unsafe ",
1384             hir::Unsafety::Normal => "",
1385         }
1386     }
1387 }
1388
1389 impl PrintWithSpace for hir::IsAsync {
1390     fn print_with_space(&self) -> &str {
1391         match self {
1392             hir::IsAsync::Async => "async ",
1393             hir::IsAsync::NotAsync => "",
1394         }
1395     }
1396 }
1397
1398 impl PrintWithSpace for hir::Mutability {
1399     fn print_with_space(&self) -> &str {
1400         match self {
1401             hir::Mutability::Not => "",
1402             hir::Mutability::Mut => "mut ",
1403         }
1404     }
1405 }
1406
1407 pub(crate) fn print_constness_with_space(
1408     c: &hir::Constness,
1409     s: Option<ConstStability>,
1410 ) -> &'static str {
1411     match (c, s) {
1412         // const stable or when feature(staged_api) is not set
1413         (
1414             hir::Constness::Const,
1415             Some(ConstStability { level: StabilityLevel::Stable { .. }, .. }),
1416         )
1417         | (hir::Constness::Const, None) => "const ",
1418         // const unstable or not const
1419         _ => "",
1420     }
1421 }
1422
1423 impl clean::Import {
1424     pub(crate) fn print<'a, 'tcx: 'a>(
1425         &'a self,
1426         cx: &'a Context<'tcx>,
1427     ) -> impl fmt::Display + 'a + Captures<'tcx> {
1428         display_fn(move |f| match self.kind {
1429             clean::ImportKind::Simple(name) => {
1430                 if name == self.source.path.last() {
1431                     write!(f, "use {};", self.source.print(cx))
1432                 } else {
1433                     write!(f, "use {} as {};", self.source.print(cx), name)
1434                 }
1435             }
1436             clean::ImportKind::Glob => {
1437                 if self.source.path.segments.is_empty() {
1438                     write!(f, "use *;")
1439                 } else {
1440                     write!(f, "use {}::*;", self.source.print(cx))
1441                 }
1442             }
1443         })
1444     }
1445 }
1446
1447 impl clean::ImportSource {
1448     pub(crate) fn print<'a, 'tcx: 'a>(
1449         &'a self,
1450         cx: &'a Context<'tcx>,
1451     ) -> impl fmt::Display + 'a + Captures<'tcx> {
1452         display_fn(move |f| match self.did {
1453             Some(did) => resolved_path(f, did, &self.path, true, false, cx),
1454             _ => {
1455                 for seg in &self.path.segments[..self.path.segments.len() - 1] {
1456                     write!(f, "{}::", seg.name)?;
1457                 }
1458                 let name = self.path.last();
1459                 if let hir::def::Res::PrimTy(p) = self.path.res {
1460                     primitive_link(f, PrimitiveType::from(p), name.as_str(), cx)?;
1461                 } else {
1462                     write!(f, "{}", name)?;
1463                 }
1464                 Ok(())
1465             }
1466         })
1467     }
1468 }
1469
1470 impl clean::TypeBinding {
1471     pub(crate) fn print<'a, 'tcx: 'a>(
1472         &'a self,
1473         cx: &'a Context<'tcx>,
1474     ) -> impl fmt::Display + 'a + Captures<'tcx> {
1475         display_fn(move |f| {
1476             f.write_str(self.assoc.name.as_str())?;
1477             if f.alternate() {
1478                 write!(f, "{:#}", self.assoc.args.print(cx))?;
1479             } else {
1480                 write!(f, "{}", self.assoc.args.print(cx))?;
1481             }
1482             match self.kind {
1483                 clean::TypeBindingKind::Equality { ref term } => {
1484                     if f.alternate() {
1485                         write!(f, " = {:#}", term.print(cx))?;
1486                     } else {
1487                         write!(f, " = {}", term.print(cx))?;
1488                     }
1489                 }
1490                 clean::TypeBindingKind::Constraint { ref bounds } => {
1491                     if !bounds.is_empty() {
1492                         if f.alternate() {
1493                             write!(f, ": {:#}", print_generic_bounds(bounds, cx))?;
1494                         } else {
1495                             write!(f, ":&nbsp;{}", print_generic_bounds(bounds, cx))?;
1496                         }
1497                     }
1498                 }
1499             }
1500             Ok(())
1501         })
1502     }
1503 }
1504
1505 pub(crate) fn print_abi_with_space(abi: Abi) -> impl fmt::Display {
1506     display_fn(move |f| {
1507         let quot = if f.alternate() { "\"" } else { "&quot;" };
1508         match abi {
1509             Abi::Rust => Ok(()),
1510             abi => write!(f, "extern {0}{1}{0} ", quot, abi.name()),
1511         }
1512     })
1513 }
1514
1515 pub(crate) fn print_default_space<'a>(v: bool) -> &'a str {
1516     if v { "default " } else { "" }
1517 }
1518
1519 impl clean::GenericArg {
1520     pub(crate) fn print<'a, 'tcx: 'a>(
1521         &'a self,
1522         cx: &'a Context<'tcx>,
1523     ) -> impl fmt::Display + 'a + Captures<'tcx> {
1524         display_fn(move |f| match self {
1525             clean::GenericArg::Lifetime(lt) => fmt::Display::fmt(&lt.print(), f),
1526             clean::GenericArg::Type(ty) => fmt::Display::fmt(&ty.print(cx), f),
1527             clean::GenericArg::Const(ct) => fmt::Display::fmt(&ct.print(cx.tcx()), f),
1528             clean::GenericArg::Infer => fmt::Display::fmt("_", f),
1529         })
1530     }
1531 }
1532
1533 impl clean::types::Term {
1534     pub(crate) fn print<'a, 'tcx: 'a>(
1535         &'a self,
1536         cx: &'a Context<'tcx>,
1537     ) -> impl fmt::Display + 'a + Captures<'tcx> {
1538         match self {
1539             clean::types::Term::Type(ty) => ty.print(cx),
1540             _ => todo!(),
1541         }
1542     }
1543 }
1544
1545 pub(crate) fn display_fn(
1546     f: impl FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result,
1547 ) -> impl fmt::Display {
1548     struct WithFormatter<F>(Cell<Option<F>>);
1549
1550     impl<F> fmt::Display for WithFormatter<F>
1551     where
1552         F: FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result,
1553     {
1554         fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1555             (self.0.take()).unwrap()(f)
1556         }
1557     }
1558
1559     WithFormatter(Cell::new(Some(f)))
1560 }