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
  12 use rustc::hir::def_id::DefId;
  13 use rustc::util::nodemap::FxHashSet;
  14 use rustc_target::spec::abi::Abi;
  15 use rustc::hir;
  16
  17 use crate::clean::{self, PrimitiveType};
  18 use crate::html::item_type::ItemType;
  19 use crate::html::render::{self, cache, CURRENT_DEPTH};
  20
  21 pub trait Print {
  22     fn print(self, buffer: &mut Buffer);
  23 }
  24
  25 impl<F> Print for F
  26     where F: FnOnce(&mut Buffer),
  27 {
  28     fn print(self, buffer: &mut Buffer) {
  29         (self)(buffer)
  30     }
  31 }
  32
  33 impl Print for String {
  34     fn print(self, buffer: &mut Buffer) {
  35         buffer.write_str(&self);
  36     }
  37 }
  38
  39 impl Print for &'_ str {
  40     fn print(self, buffer: &mut Buffer) {
  41         buffer.write_str(self);
  42     }
  43 }
  44
  45 #[derive(Debug, Clone)]
  46 pub struct Buffer {
  47     for_html: bool,
  48     buffer: String,
  49 }
  50
  51 impl Buffer {
  52     crate fn empty_from(v: &Buffer) -> Buffer {
  53         Buffer {
  54             for_html: v.for_html,
  55             buffer: String::new(),
  56         }
  57     }
  58
  59     crate fn html() -> Buffer {
  60         Buffer {
  61             for_html: true,
  62             buffer: String::new(),
  63         }
  64     }
  65
  66     crate fn new() -> Buffer {
  67         Buffer {
  68             for_html: false,
  69             buffer: String::new(),
  70         }
  71     }
  72
  73     crate fn is_empty(&self) -> bool {
  74         self.buffer.is_empty()
  75     }
  76
  77     crate fn into_inner(self) -> String {
  78         self.buffer
  79     }
  80
  81     crate fn insert_str(&mut self, idx: usize, s: &str) {
  82         self.buffer.insert_str(idx, s);
  83     }
  84
  85     crate fn push_str(&mut self, s: &str) {
  86         self.buffer.push_str(s);
  87     }
  88
  89     // Intended for consumption by write! and writeln! (std::fmt) but without
  90     // the fmt::Result return type imposed by fmt::Write (and avoiding the trait
  91     // import).
  92     crate fn write_str(&mut self, s: &str) {
  93         self.buffer.push_str(s);
  94     }
  95
  96     // Intended for consumption by write! and writeln! (std::fmt) but without
  97     // the fmt::Result return type imposed by fmt::Write (and avoiding the trait
  98     // import).
  99     crate fn write_fmt(&mut self, v: fmt::Arguments<'_>) {
 100         use fmt::Write;
 101         self.buffer.write_fmt(v).unwrap();
 102     }
 103
 104     crate fn to_display<T: Print>(mut self, t: T) -> String {
 105         t.print(&mut self);
 106         self.into_inner()
 107     }
 108
 109     crate fn from_display<T: std::fmt::Display>(&mut self, t: T) {
 110         if self.for_html {
 111             write!(self, "{}", t);
 112         } else {
 113             write!(self, "{:#}", t);
 114         }
 115     }
 116
 117     crate fn is_for_html(&self) -> bool {
 118         self.for_html
 119     }
 120 }
 121
 122 /// Wrapper struct for properly emitting a function or method declaration.
 123 pub struct Function<'a> {
 124     /// The declaration to emit.
 125     pub decl: &'a clean::FnDecl,
 126     /// The length of the function header and name. In other words, the number of characters in the
 127     /// function declaration up to but not including the parentheses.
 128     ///
 129     /// Used to determine line-wrapping.
 130     pub header_len: usize,
 131     /// The number of spaces to indent each successive line with, if line-wrapping is necessary.
 132     pub indent: usize,
 133     /// Whether the function is async or not.
 134     pub asyncness: hir::IsAsync,
 135 }
 136
 137 /// Wrapper struct for emitting a where-clause from Generics.
 138 pub struct WhereClause<'a>{
 139     /// The Generics from which to emit a where-clause.
 140     pub gens: &'a clean::Generics,
 141     /// The number of spaces to indent each line with.
 142     pub indent: usize,
 143     /// Whether the where-clause needs to add a comma and newline after the last bound.
 144     pub end_newline: bool,
 145 }
 146
 147 fn comma_sep<T: fmt::Display>(items: impl Iterator<Item=T>) -> impl fmt::Display {
 148     display_fn(move |f| {
 149         for (i, item) in items.enumerate() {
 150             if i != 0 { write!(f, ", ")?; }
 151             fmt::Display::fmt(&item, f)?;
 152         }
 153         Ok(())
 154     })
 155 }
 156
 157 crate fn print_generic_bounds(bounds: &[clean::GenericBound]) -> impl fmt::Display + '_ {
 158     display_fn(move |f| {
 159         let mut bounds_dup = FxHashSet::default();
 160
 161         for (i, bound) in bounds.iter().filter(|b| {
 162             bounds_dup.insert(b.print().to_string())
 163         }).enumerate() {
 164             if i > 0 {
 165                 f.write_str(" + ")?;
 166             }
 167             fmt::Display::fmt(&bound.print(), f)?;
 168         }
 169         Ok(())
 170     })
 171 }
 172
 173 impl clean::GenericParamDef {
 174     crate fn print(&self) -> impl fmt::Display + '_ {
 175         display_fn(move |f| {
 176             match self.kind {
 177                 clean::GenericParamDefKind::Lifetime => write!(f, "{}", self.name),
 178                 clean::GenericParamDefKind::Type { ref bounds, ref default, .. } => {
 179                     f.write_str(&self.name)?;
 180
 181                     if !bounds.is_empty() {
 182                         if f.alternate() {
 183                             write!(f, ": {:#}", print_generic_bounds(bounds))?;
 184                         } else {
 185                             write!(f, ":&nbsp;{}", print_generic_bounds(bounds))?;
 186                         }
 187                     }
 188
 189                     if let Some(ref ty) = default {
 190                         if f.alternate() {
 191                             write!(f, " = {:#}", ty.print())?;
 192                         } else {
 193                             write!(f, "&nbsp;=&nbsp;{}", ty.print())?;
 194                         }
 195                     }
 196
 197                     Ok(())
 198                 }
 199                 clean::GenericParamDefKind::Const { ref ty, .. } => {
 200                     f.write_str("const ")?;
 201                     f.write_str(&self.name)?;
 202
 203                     if f.alternate() {
 204                         write!(f, ": {:#}", ty.print())
 205                     } else {
 206                         write!(f, ":&nbsp;{}", ty.print())
 207                     }
 208                 }
 209             }
 210         })
 211     }
 212 }
 213
 214 impl clean::Generics {
 215     crate fn print(&self) -> impl fmt::Display + '_ {
 216         display_fn(move |f| {
 217             let real_params = self.params
 218                 .iter()
 219                 .filter(|p| !p.is_synthetic_type_param())
 220                 .collect::<Vec<_>>();
 221             if real_params.is_empty() {
 222                 return Ok(());
 223             }
 224             if f.alternate() {
 225                 write!(f, "<{:#}>", comma_sep(real_params.iter().map(|g| g.print())))
 226             } else {
 227                 write!(f, "&lt;{}&gt;", comma_sep(real_params.iter().map(|g| g.print())))
 228             }
 229         })
 230     }
 231 }
 232
 233 impl<'a> fmt::Display for WhereClause<'a> {
 234     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 235         let &WhereClause { gens, indent, end_newline } = self;
 236         if gens.where_predicates.is_empty() {
 237             return Ok(());
 238         }
 239         let mut clause = String::new();
 240         if f.alternate() {
 241             clause.push_str(" where");
 242         } else {
 243             if end_newline {
 244                 clause.push_str(" <span class=\"where fmt-newline\">where");
 245             } else {
 246                 clause.push_str(" <span class=\"where\">where");
 247             }
 248         }
 249         for (i, pred) in gens.where_predicates.iter().enumerate() {
 250             if f.alternate() {
 251                 clause.push(' ');
 252             } else {
 253                 clause.push_str("<br>");
 254             }
 255
 256             match pred {
 257                 &clean::WherePredicate::BoundPredicate { ref ty, ref bounds } => {
 258                     let bounds = bounds;
 259                     if f.alternate() {
 260                         clause.push_str(&format!("{:#}: {:#}",
 261                                 ty.print(), print_generic_bounds(bounds)));
 262                     } else {
 263                         clause.push_str(&format!("{}: {}",
 264                                 ty.print(), print_generic_bounds(bounds)));
 265                     }
 266                 }
 267                 &clean::WherePredicate::RegionPredicate { ref lifetime, ref bounds } => {
 268                     clause.push_str(&format!("{}: {}",
 269                                                 lifetime.print(),
 270                                                 bounds.iter()
 271                                                     .map(|b| b.print().to_string())
 272                                                     .collect::<Vec<_>>()
 273                                                     .join(" + ")));
 274                 }
 275                 &clean::WherePredicate::EqPredicate { ref lhs, ref rhs } => {
 276                     if f.alternate() {
 277                         clause.push_str(&format!("{:#} == {:#}", lhs.print(), rhs.print()));
 278                     } else {
 279                         clause.push_str(&format!("{} == {}", lhs.print(), rhs.print()));
 280                     }
 281                 }
 282             }
 283
 284             if i < gens.where_predicates.len() - 1 || end_newline {
 285                 clause.push(',');
 286             }
 287         }
 288
 289         if end_newline {
 290             // add a space so stripping <br> tags and breaking spaces still renders properly
 291             if f.alternate() {
 292                 clause.push(' ');
 293             } else {
 294                 clause.push_str("&nbsp;");
 295             }
 296         }
 297
 298         if !f.alternate() {
 299             clause.push_str("</span>");
 300             let padding = "&nbsp;".repeat(indent + 4);
 301             clause = clause.replace("<br>", &format!("<br>{}", padding));
 302             clause.insert_str(0, &"&nbsp;".repeat(indent.saturating_sub(1)));
 303             if !end_newline {
 304                 clause.insert_str(0, "<br>");
 305             }
 306         }
 307         write!(f, "{}", clause)
 308     }
 309 }
 310
 311 impl clean::Lifetime {
 312     crate fn print(&self) -> &str {
 313         self.get_ref()
 314     }
 315 }
 316
 317 impl clean::Constant {
 318     crate fn print(&self) -> &str {
 319         &self.expr
 320     }
 321 }
 322
 323 impl clean::PolyTrait {
 324     fn print(&self) -> impl fmt::Display + '_ {
 325         display_fn(move |f| {
 326             if !self.generic_params.is_empty() {
 327                 if f.alternate() {
 328                     write!(f, "for<{:#}> ",
 329                         comma_sep(self.generic_params.iter().map(|g| g.print())))?;
 330                 } else {
 331                     write!(f, "for&lt;{}&gt; ",
 332                         comma_sep(self.generic_params.iter().map(|g| g.print())))?;
 333                 }
 334             }
 335             if f.alternate() {
 336                 write!(f, "{:#}", self.trait_.print())
 337             } else {
 338                 write!(f, "{}", self.trait_.print())
 339             }
 340         })
 341     }
 342 }
 343
 344 impl clean::GenericBound {
 345     crate fn print(&self) -> impl fmt::Display + '_ {
 346         display_fn(move |f| {
 347             match self {
 348                 clean::GenericBound::Outlives(lt) => {
 349                     write!(f, "{}", lt.print())
 350                 }
 351                 clean::GenericBound::TraitBound(ty, modifier) => {
 352                     let modifier_str = match modifier {
 353                         hir::TraitBoundModifier::None => "",
 354                         hir::TraitBoundModifier::Maybe => "?",
 355                     };
 356                     if f.alternate() {
 357                         write!(f, "{}{:#}", modifier_str, ty.print())
 358                     } else {
 359                         write!(f, "{}{}", modifier_str, ty.print())
 360                     }
 361                 }
 362             }
 363         })
 364     }
 365 }
 366
 367 impl clean::GenericArgs {
 368     fn print(&self) -> impl fmt::Display + '_ {
 369         display_fn(move |f| {
 370             match *self {
 371                 clean::GenericArgs::AngleBracketed { ref args, ref bindings } => {
 372                     if !args.is_empty() || !bindings.is_empty() {
 373                         if f.alternate() {
 374                             f.write_str("<")?;
 375                         } else {
 376                             f.write_str("&lt;")?;
 377                         }
 378                         let mut comma = false;
 379                         for arg in args {
 380                             if comma {
 381                                 f.write_str(", ")?;
 382                             }
 383                             comma = true;
 384                             if f.alternate() {
 385                                 write!(f, "{:#}", arg.print())?;
 386                             } else {
 387                                 write!(f, "{}", arg.print())?;
 388                             }
 389                         }
 390                         for binding in bindings {
 391                             if comma {
 392                                 f.write_str(", ")?;
 393                             }
 394                             comma = true;
 395                             if f.alternate() {
 396                                 write!(f, "{:#}", binding.print())?;
 397                             } else {
 398                                 write!(f, "{}", binding.print())?;
 399                             }
 400                         }
 401                         if f.alternate() {
 402                             f.write_str(">")?;
 403                         } else {
 404                             f.write_str("&gt;")?;
 405                         }
 406                     }
 407                 }
 408                 clean::GenericArgs::Parenthesized { ref inputs, ref output } => {
 409                     f.write_str("(")?;
 410                     let mut comma = false;
 411                     for ty in inputs {
 412                         if comma {
 413                             f.write_str(", ")?;
 414                         }
 415                         comma = true;
 416                         if f.alternate() {
 417                             write!(f, "{:#}", ty.print())?;
 418                         } else {
 419                             write!(f, "{}", ty.print())?;
 420                         }
 421                     }
 422                     f.write_str(")")?;
 423                     if let Some(ref ty) = *output {
 424                         if f.alternate() {
 425                             write!(f, " -> {:#}", ty.print())?;
 426                         } else {
 427                             write!(f, " -&gt; {}", ty.print())?;
 428                         }
 429                     }
 430                 }
 431             }
 432             Ok(())
 433         })
 434     }
 435 }
 436
 437 impl clean::PathSegment {
 438     crate fn print(&self) -> impl fmt::Display + '_ {
 439         display_fn(move |f| {
 440             f.write_str(&self.name)?;
 441             if f.alternate() {
 442                 write!(f, "{:#}", self.args.print())
 443             } else {
 444                 write!(f, "{}", self.args.print())
 445             }
 446         })
 447     }
 448 }
 449
 450 impl clean::Path {
 451     crate fn print(&self) -> impl fmt::Display + '_ {
 452         display_fn(move |f| {
 453             if self.global {
 454                 f.write_str("::")?
 455             }
 456
 457             for (i, seg) in self.segments.iter().enumerate() {
 458                 if i > 0 {
 459                     f.write_str("::")?
 460                 }
 461                 if f.alternate() {
 462                     write!(f, "{:#}", seg.print())?;
 463                 } else {
 464                     write!(f, "{}", seg.print())?;
 465                 }
 466             }
 467             Ok(())
 468         })
 469     }
 470 }
 471
 472 pub fn href(did: DefId) -> Option<(String, ItemType, Vec<String>)> {
 473     let cache = cache();
 474     if !did.is_local() && !cache.access_levels.is_public(did) {
 475         return None
 476     }
 477
 478     let depth = CURRENT_DEPTH.with(|l| l.get());
 479     let (fqp, shortty, mut url) = match cache.paths.get(&did) {
 480         Some(&(ref fqp, shortty)) => {
 481             (fqp, shortty, "../".repeat(depth))
 482         }
 483         None => {
 484             let &(ref fqp, shortty) = cache.external_paths.get(&did)?;
 485             (fqp, shortty, match cache.extern_locations[&did.krate] {
 486                 (.., render::Remote(ref s)) => s.to_string(),
 487                 (.., render::Local) => "../".repeat(depth),
 488                 (.., render::Unknown) => return None,
 489             })
 490         }
 491     };
 492     for component in &fqp[..fqp.len() - 1] {
 493         url.push_str(component);
 494         url.push_str("/");
 495     }
 496     match shortty {
 497         ItemType::Module => {
 498             url.push_str(fqp.last().unwrap());
 499             url.push_str("/index.html");
 500         }
 501         _ => {
 502             url.push_str(shortty.as_str());
 503             url.push_str(".");
 504             url.push_str(fqp.last().unwrap());
 505             url.push_str(".html");
 506         }
 507     }
 508     Some((url, shortty, fqp.to_vec()))
 509 }
 510
 511 /// Used when rendering a `ResolvedPath` structure. This invokes the `path`
 512 /// rendering function with the necessary arguments for linking to a local path.
 513 fn resolved_path(w: &mut fmt::Formatter<'_>, did: DefId, path: &clean::Path,
 514                  print_all: bool, use_absolute: bool) -> fmt::Result {
 515     let last = path.segments.last().unwrap();
 516
 517     if print_all {
 518         for seg in &path.segments[..path.segments.len() - 1] {
 519             write!(w, "{}::", seg.name)?;
 520         }
 521     }
 522     if w.alternate() {
 523         write!(w, "{}{:#}", &last.name, last.args.print())?;
 524     } else {
 525         let path = if use_absolute {
 526             if let Some((_, _, fqp)) = href(did) {
 527                 format!("{}::{}",
 528                         fqp[..fqp.len() - 1].join("::"),
 529                         anchor(did, fqp.last().unwrap()))
 530             } else {
 531                 last.name.to_string()
 532             }
 533         } else {
 534             anchor(did, &last.name).to_string()
 535         };
 536         write!(w, "{}{}", path, last.args.print())?;
 537     }
 538     Ok(())
 539 }
 540
 541 fn primitive_link(f: &mut fmt::Formatter<'_>,
 542                   prim: clean::PrimitiveType,
 543                   name: &str) -> fmt::Result {
 544     let m = cache();
 545     let mut needs_termination = false;
 546     if !f.alternate() {
 547         match m.primitive_locations.get(&prim) {
 548             Some(&def_id) if def_id.is_local() => {
 549                 let len = CURRENT_DEPTH.with(|s| s.get());
 550                 let len = if len == 0 {0} else {len - 1};
 551                 write!(f, "<a class=\"primitive\" href=\"{}primitive.{}.html\">",
 552                        "../".repeat(len),
 553                        prim.to_url_str())?;
 554                 needs_termination = true;
 555             }
 556             Some(&def_id) => {
 557                 let loc = match m.extern_locations[&def_id.krate] {
 558                     (ref cname, _, render::Remote(ref s)) => {
 559                         Some((cname, s.to_string()))
 560                     }
 561                     (ref cname, _, render::Local) => {
 562                         let len = CURRENT_DEPTH.with(|s| s.get());
 563                         Some((cname, "../".repeat(len)))
 564                     }
 565                     (.., render::Unknown) => None,
 566                 };
 567                 if let Some((cname, root)) = loc {
 568                     write!(f, "<a class=\"primitive\" href=\"{}{}/primitive.{}.html\">",
 569                            root,
 570                            cname,
 571                            prim.to_url_str())?;
 572                     needs_termination = true;
 573                 }
 574             }
 575             None => {}
 576         }
 577     }
 578     write!(f, "{}", name)?;
 579     if needs_termination {
 580         write!(f, "</a>")?;
 581     }
 582     Ok(())
 583 }
 584
 585 /// Helper to render type parameters
 586 fn tybounds(param_names: &Option<Vec<clean::GenericBound>>) -> impl fmt::Display + '_ {
 587     display_fn(move |f| {
 588         match *param_names {
 589             Some(ref params) => {
 590                 for param in params {
 591                     write!(f, " + ")?;
 592                     fmt::Display::fmt(&param.print(), f)?;
 593                 }
 594                 Ok(())
 595             }
 596             None => Ok(())
 597         }
 598     })
 599 }
 600
 601 pub fn anchor(did: DefId, text: &str) -> impl fmt::Display + '_ {
 602     display_fn(move |f| {
 603         if let Some((url, short_ty, fqp)) = href(did) {
 604             write!(f, r#"<a class="{}" href="{}" title="{} {}">{}</a>"#,
 605                 short_ty, url, short_ty, fqp.join("::"), text)
 606         } else {
 607             write!(f, "{}", text)
 608         }
 609     })
 610 }
 611
 612 fn fmt_type(t: &clean::Type, f: &mut fmt::Formatter<'_>, use_absolute: bool) -> fmt::Result {
 613     match *t {
 614         clean::Generic(ref name) => {
 615             f.write_str(name)
 616         }
 617         clean::ResolvedPath{ did, ref param_names, ref path, is_generic } => {
 618             if param_names.is_some() {
 619                 f.write_str("dyn ")?;
 620             }
 621             // Paths like `T::Output` and `Self::Output` should be rendered with all segments.
 622             resolved_path(f, did, path, is_generic, use_absolute)?;
 623             fmt::Display::fmt(&tybounds(param_names), f)
 624         }
 625         clean::Infer => write!(f, "_"),
 626         clean::Primitive(prim) => primitive_link(f, prim, prim.as_str()),
 627         clean::BareFunction(ref decl) => {
 628             if f.alternate() {
 629                 write!(f, "{}{:#}fn{:#}{:#}",
 630                        decl.unsafety.print_with_space(),
 631                        print_abi_with_space(decl.abi),
 632                        decl.print_generic_params(),
 633                        decl.decl.print())
 634             } else {
 635                 write!(f, "{}{}",
 636                     decl.unsafety.print_with_space(), print_abi_with_space(decl.abi))?;
 637                 primitive_link(f, PrimitiveType::Fn, "fn")?;
 638                 write!(f, "{}{}", decl.print_generic_params(), decl.decl.print())
 639             }
 640         }
 641         clean::Tuple(ref typs) => {
 642             match &typs[..] {
 643                 &[] => primitive_link(f, PrimitiveType::Unit, "()"),
 644                 &[ref one] => {
 645                     primitive_link(f, PrimitiveType::Tuple, "(")?;
 646                     // Carry `f.alternate()` into this display w/o branching manually.
 647                     fmt::Display::fmt(&one.print(), f)?;
 648                     primitive_link(f, PrimitiveType::Tuple, ",)")
 649                 }
 650                 many => {
 651                     primitive_link(f, PrimitiveType::Tuple, "(")?;
 652                     for (i, item) in many.iter().enumerate() {
 653                         if i != 0 { write!(f, ", ")?; }
 654                         fmt::Display::fmt(&item.print(), f)?;
 655                     }
 656                     primitive_link(f, PrimitiveType::Tuple, ")")
 657                 }
 658             }
 659         }
 660         clean::Slice(ref t) => {
 661             primitive_link(f, PrimitiveType::Slice, "[")?;
 662             fmt::Display::fmt(&t.print(), f)?;
 663             primitive_link(f, PrimitiveType::Slice, "]")
 664         }
 665         clean::Array(ref t, ref n) => {
 666             primitive_link(f, PrimitiveType::Array, "[")?;
 667             fmt::Display::fmt(&t.print(), f)?;
 668             primitive_link(f, PrimitiveType::Array, &format!("; {}]", n))
 669         }
 670         clean::Never => primitive_link(f, PrimitiveType::Never, "!"),
 671         clean::RawPointer(m, ref t) => {
 672             let m = match m {
 673                 clean::Immutable => "const",
 674                 clean::Mutable => "mut",
 675             };
 676             match **t {
 677                 clean::Generic(_) | clean::ResolvedPath {is_generic: true, ..} => {
 678                     if f.alternate() {
 679                         primitive_link(f, clean::PrimitiveType::RawPointer,
 680                                        &format!("*{} {:#}", m, t.print()))
 681                     } else {
 682                         primitive_link(f, clean::PrimitiveType::RawPointer,
 683                                        &format!("*{} {}", m, t.print()))
 684                     }
 685                 }
 686                 _ => {
 687                     primitive_link(f, clean::PrimitiveType::RawPointer, &format!("*{} ", m))?;
 688                     fmt::Display::fmt(&t.print(), f)
 689                 }
 690             }
 691         }
 692         clean::BorrowedRef{ lifetime: ref l, mutability, type_: ref ty} => {
 693             let lt = match l {
 694                 Some(l) => format!("{} ", l.print()),
 695                 _ => String::new()
 696             };
 697             let m = mutability.print_with_space();
 698             let amp = if f.alternate() {
 699                 "&".to_string()
 700             } else {
 701                 "&amp;".to_string()
 702             };
 703             match **ty {
 704                 clean::Slice(ref bt) => { // `BorrowedRef{ ... Slice(T) }` is `&[T]`
 705                     match **bt {
 706                         clean::Generic(_) => {
 707                             if f.alternate() {
 708                                 primitive_link(f, PrimitiveType::Slice,
 709                                     &format!("{}{}{}[{:#}]", amp, lt, m, bt.print()))
 710                             } else {
 711                                 primitive_link(f, PrimitiveType::Slice,
 712                                     &format!("{}{}{}[{}]", amp, lt, m, bt.print()))
 713                             }
 714                         }
 715                         _ => {
 716                             primitive_link(f, PrimitiveType::Slice,
 717                                            &format!("{}{}{}[", amp, lt, m))?;
 718                             if f.alternate() {
 719                                 write!(f, "{:#}", bt.print())?;
 720                             } else {
 721                                 write!(f, "{}", bt.print())?;
 722                             }
 723                             primitive_link(f, PrimitiveType::Slice, "]")
 724                         }
 725                     }
 726                 }
 727                 clean::ResolvedPath { param_names: Some(ref v), .. } if !v.is_empty() => {
 728                     write!(f, "{}{}{}(", amp, lt, m)?;
 729                     fmt_type(&ty, f, use_absolute)?;
 730                     write!(f, ")")
 731                 }
 732                 clean::Generic(..) => {
 733                     primitive_link(f, PrimitiveType::Reference,
 734                                    &format!("{}{}{}", amp, lt, m))?;
 735                     fmt_type(&ty, f, use_absolute)
 736                 }
 737                 _ => {
 738                     write!(f, "{}{}{}", amp, lt, m)?;
 739                     fmt_type(&ty, f, use_absolute)
 740                 }
 741             }
 742         }
 743         clean::ImplTrait(ref bounds) => {
 744             if f.alternate() {
 745                 write!(f, "impl {:#}", print_generic_bounds(bounds))
 746             } else {
 747                 write!(f, "impl {}", print_generic_bounds(bounds))
 748             }
 749         }
 750         clean::QPath { ref name, ref self_type, ref trait_ } => {
 751             let should_show_cast = match *trait_ {
 752                 box clean::ResolvedPath { ref path, .. } => {
 753                     !path.segments.is_empty() && !self_type.is_self_type()
 754                 }
 755                 _ => true,
 756             };
 757             if f.alternate() {
 758                 if should_show_cast {
 759                     write!(f, "<{:#} as {:#}>::", self_type.print(), trait_.print())?
 760                 } else {
 761                     write!(f, "{:#}::", self_type.print())?
 762                 }
 763             } else {
 764                 if should_show_cast {
 765                     write!(f, "&lt;{} as {}&gt;::", self_type.print(), trait_.print())?
 766                 } else {
 767                     write!(f, "{}::", self_type.print())?
 768                 }
 769             };
 770             match *trait_ {
 771                 // It's pretty unsightly to look at `<A as B>::C` in output, and
 772                 // we've got hyperlinking on our side, so try to avoid longer
 773                 // notation as much as possible by making `C` a hyperlink to trait
 774                 // `B` to disambiguate.
 775                 //
 776                 // FIXME: this is still a lossy conversion and there should probably
 777                 //        be a better way of representing this in general? Most of
 778                 //        the ugliness comes from inlining across crates where
 779                 //        everything comes in as a fully resolved QPath (hard to
 780                 //        look at).
 781                 box clean::ResolvedPath { did, ref param_names, .. } => {
 782                     match href(did) {
 783                         Some((ref url, _, ref path)) if !f.alternate() => {
 784                             write!(f,
 785                                    "<a class=\"type\" href=\"{url}#{shortty}.{name}\" \
 786                                    title=\"type {path}::{name}\">{name}</a>",
 787                                    url = url,
 788                                    shortty = ItemType::AssocType,
 789                                    name = name,
 790                                    path = path.join("::"))?;
 791                         }
 792                         _ => write!(f, "{}", name)?,
 793                     }
 794
 795                     // FIXME: `param_names` are not rendered, and this seems bad?
 796                     drop(param_names);
 797                     Ok(())
 798                 }
 799                 _ => {
 800                     write!(f, "{}", name)
 801                 }
 802             }
 803         }
 804     }
 805 }
 806
 807 impl clean::Type {
 808     crate fn print(&self) -> impl fmt::Display + '_ {
 809         display_fn(move |f| {
 810             fmt_type(self, f, false)
 811         })
 812     }
 813 }
 814
 815 impl clean::Impl {
 816     crate fn print(&self) -> impl fmt::Display + '_ {
 817         self.print_inner(true, false)
 818     }
 819
 820     fn print_inner(
 821         &self,
 822         link_trait: bool,
 823         use_absolute: bool,
 824     ) -> impl fmt::Display + '_ {
 825         display_fn(move |f| {
 826             if f.alternate() {
 827                 write!(f, "impl{:#} ", self.generics.print())?;
 828             } else {
 829                 write!(f, "impl{} ", self.generics.print())?;
 830             }
 831
 832             if let Some(ref ty) = self.trait_ {
 833                 if self.polarity == Some(clean::ImplPolarity::Negative) {
 834                     write!(f, "!")?;
 835                 }
 836
 837                 if link_trait {
 838                     fmt::Display::fmt(&ty.print(), f)?;
 839                 } else {
 840                     match ty {
 841                         clean::ResolvedPath { param_names: None, path, is_generic: false, .. } => {
 842                             let last = path.segments.last().unwrap();
 843                             fmt::Display::fmt(&last.name, f)?;
 844                             fmt::Display::fmt(&last.args.print(), f)?;
 845                         }
 846                         _ => unreachable!(),
 847                     }
 848                 }
 849                 write!(f, " for ")?;
 850             }
 851
 852             if let Some(ref ty) = self.blanket_impl {
 853                 fmt_type(ty, f, use_absolute)?;
 854             } else {
 855                 fmt_type(&self.for_, f, use_absolute)?;
 856             }
 857
 858             fmt::Display::fmt(&WhereClause {
 859                 gens: &self.generics,
 860                 indent: 0,
 861                 end_newline: true,
 862             }, f)?;
 863             Ok(())
 864         })
 865     }
 866 }
 867
 868 // The difference from above is that trait is not hyperlinked.
 869 pub fn fmt_impl_for_trait_page(i: &clean::Impl,
 870                                f: &mut Buffer,
 871                                use_absolute: bool) {
 872     f.from_display(i.print_inner(false, use_absolute))
 873 }
 874
 875 impl clean::Arguments {
 876     crate fn print(&self) -> impl fmt::Display + '_ {
 877         display_fn(move |f| {
 878             for (i, input) in self.values.iter().enumerate() {
 879                 if !input.name.is_empty() {
 880                     write!(f, "{}: ", input.name)?;
 881                 }
 882                 if f.alternate() {
 883                     write!(f, "{:#}", input.type_.print())?;
 884                 } else {
 885                     write!(f, "{}", input.type_.print())?;
 886                 }
 887                 if i + 1 < self.values.len() { write!(f, ", ")?; }
 888             }
 889             Ok(())
 890         })
 891     }
 892 }
 893
 894 impl clean::FunctionRetTy {
 895     crate fn print(&self) -> impl fmt::Display + '_ {
 896         display_fn(move |f| {
 897             match self {
 898                 clean::Return(clean::Tuple(tys)) if tys.is_empty() => Ok(()),
 899                 clean::Return(ty) if f.alternate() => write!(f, " -> {:#}", ty.print()),
 900                 clean::Return(ty) => write!(f, " -&gt; {}", ty.print()),
 901                 clean::DefaultReturn => Ok(()),
 902             }
 903         })
 904     }
 905 }
 906
 907 impl clean::BareFunctionDecl {
 908     fn print_generic_params(&self) -> impl fmt::Display + '_ {
 909         comma_sep(self.generic_params.iter().map(|g| g.print()))
 910     }
 911 }
 912
 913 impl clean::FnDecl {
 914     crate fn print(&self) -> impl fmt::Display + '_ {
 915         display_fn(move |f| {
 916         let ellipsis = if self.c_variadic { ", ..." } else { "" };
 917             if f.alternate() {
 918                 write!(f,
 919                     "({args:#}{ellipsis}){arrow:#}",
 920                     args = self.inputs.print(), ellipsis = ellipsis, arrow = self.output.print())
 921             } else {
 922                 write!(f,
 923                     "({args}{ellipsis}){arrow}",
 924                     args = self.inputs.print(), ellipsis = ellipsis, arrow = self.output.print())
 925             }
 926         })
 927     }
 928 }
 929
 930
 931 impl Function<'_> {
 932     crate fn print(&self) -> impl fmt::Display + '_ {
 933         display_fn(move |f| {
 934             let &Function { decl, header_len, indent, asyncness } = self;
 935             let amp = if f.alternate() { "&" } else { "&amp;" };
 936             let mut args = String::new();
 937             let mut args_plain = String::new();
 938             for (i, input) in decl.inputs.values.iter().enumerate() {
 939                 if i == 0 {
 940                     args.push_str("<br>");
 941                 }
 942
 943                 if let Some(selfty) = input.to_self() {
 944                     match selfty {
 945                         clean::SelfValue => {
 946                             args.push_str("self");
 947                             args_plain.push_str("self");
 948                         }
 949                         clean::SelfBorrowed(Some(ref lt), mtbl) => {
 950                             args.push_str(
 951                                 &format!("{}{} {}self", amp, lt.print(), mtbl.print_with_space()));
 952                             args_plain.push_str(
 953                                 &format!("&{} {}self", lt.print(), mtbl.print_with_space()));
 954                         }
 955                         clean::SelfBorrowed(None, mtbl) => {
 956                             args.push_str(&format!("{}{}self", amp, mtbl.print_with_space()));
 957                             args_plain.push_str(&format!("&{}self", mtbl.print_with_space()));
 958                         }
 959                         clean::SelfExplicit(ref typ) => {
 960                             if f.alternate() {
 961                                 args.push_str(&format!("self: {:#}", typ.print()));
 962                             } else {
 963                                 args.push_str(&format!("self: {}", typ.print()));
 964                             }
 965                             args_plain.push_str(&format!("self: {:#}", typ.print()));
 966                         }
 967                     }
 968                 } else {
 969                     if i > 0 {
 970                         args.push_str(" <br>");
 971                         args_plain.push_str(" ");
 972                     }
 973                     if !input.name.is_empty() {
 974                         args.push_str(&format!("{}: ", input.name));
 975                         args_plain.push_str(&format!("{}: ", input.name));
 976                     }
 977
 978                     if f.alternate() {
 979                         args.push_str(&format!("{:#}", input.type_.print()));
 980                     } else {
 981                         args.push_str(&input.type_.print().to_string());
 982                     }
 983                     args_plain.push_str(&format!("{:#}", input.type_.print()));
 984                 }
 985                 if i + 1 < decl.inputs.values.len() {
 986                     args.push(',');
 987                     args_plain.push(',');
 988                 }
 989             }
 990
 991             let mut args_plain = format!("({})", args_plain);
 992
 993             if decl.c_variadic {
 994                 args.push_str(",<br> ...");
 995                 args_plain.push_str(", ...");
 996             }
 997
 998             let output = if let hir::IsAsync::Async = asyncness {
 999                 Cow::Owned(decl.sugared_async_return_type())
1000             } else {
1001                 Cow::Borrowed(&decl.output)
1002             };
1003
1004             let arrow_plain = format!("{:#}", &output.print());
1005             let arrow = if f.alternate() {
1006                 format!("{:#}", &output.print())
1007             } else {
1008                 output.print().to_string()
1009             };
1010
1011             let declaration_len = header_len + args_plain.len() + arrow_plain.len();
1012             let output = if declaration_len > 80 {
1013                 let full_pad = format!("<br>{}", "&nbsp;".repeat(indent + 4));
1014                 let close_pad = format!("<br>{}", "&nbsp;".repeat(indent));
1015                 format!("({args}{close}){arrow}",
1016                         args = args.replace("<br>", &full_pad),
1017                         close = close_pad,
1018                         arrow = arrow)
1019             } else {
1020                 format!("({args}){arrow}", args = args.replace("<br>", ""), arrow = arrow)
1021             };
1022
1023             if f.alternate() {
1024                 write!(f, "{}", output.replace("<br>", "\n"))
1025             } else {
1026                 write!(f, "{}", output)
1027             }
1028         })
1029     }
1030 }
1031
1032 impl clean::Visibility {
1033     crate fn print_with_space(&self) -> impl fmt::Display + '_ {
1034         display_fn(move |f| {
1035             match *self {
1036                 clean::Public => f.write_str("pub "),
1037                 clean::Inherited => Ok(()),
1038                 clean::Visibility::Crate => write!(f, "pub(crate) "),
1039                 clean::Visibility::Restricted(did, ref path) => {
1040                     f.write_str("pub(")?;
1041                     if path.segments.len() != 1
1042                         || (path.segments[0].name != "self" && path.segments[0].name != "super")
1043                     {
1044                         f.write_str("in ")?;
1045                     }
1046                     resolved_path(f, did, path, true, false)?;
1047                     f.write_str(") ")
1048                 }
1049             }
1050         })
1051     }
1052 }
1053
1054 crate trait PrintWithSpace {
1055     fn print_with_space(&self) -> &str;
1056 }
1057
1058 impl PrintWithSpace for hir::Unsafety {
1059     fn print_with_space(&self) -> &str {
1060         match self {
1061             hir::Unsafety::Unsafe => "unsafe ",
1062             hir::Unsafety::Normal => ""
1063         }
1064     }
1065 }
1066
1067 impl PrintWithSpace for hir::Constness {
1068     fn print_with_space(&self) -> &str {
1069         match self {
1070             hir::Constness::Const => "const ",
1071             hir::Constness::NotConst => ""
1072         }
1073     }
1074 }
1075
1076 impl PrintWithSpace for hir::IsAsync {
1077     fn print_with_space(&self) -> &str {
1078         match self {
1079             hir::IsAsync::Async => "async ",
1080             hir::IsAsync::NotAsync => "",
1081         }
1082     }
1083 }
1084
1085 impl clean::Import {
1086     crate fn print(&self) -> impl fmt::Display + '_ {
1087         display_fn(move |f| {
1088             match *self {
1089                 clean::Import::Simple(ref name, ref src) => {
1090                     if *name == src.path.last_name() {
1091                         write!(f, "use {};", src.print())
1092                     } else {
1093                         write!(f, "use {} as {};", src.print(), *name)
1094                     }
1095                 }
1096                 clean::Import::Glob(ref src) => {
1097                     if src.path.segments.is_empty() {
1098                         write!(f, "use *;")
1099                     } else {
1100                         write!(f, "use {}::*;", src.print())
1101                     }
1102                 }
1103             }
1104         })
1105     }
1106 }
1107
1108 impl clean::ImportSource {
1109     crate fn print(&self) -> impl fmt::Display + '_ {
1110         display_fn(move |f| {
1111             match self.did {
1112                 Some(did) => resolved_path(f, did, &self.path, true, false),
1113                 _ => {
1114                     for (i, seg) in self.path.segments.iter().enumerate() {
1115                         if i > 0 {
1116                             write!(f, "::")?
1117                         }
1118                         write!(f, "{}", seg.name)?;
1119                     }
1120                     Ok(())
1121                 }
1122             }
1123         })
1124     }
1125 }
1126
1127 impl clean::TypeBinding {
1128     crate fn print(&self) -> impl fmt::Display + '_ {
1129         display_fn(move |f| {
1130             f.write_str(&self.name)?;
1131             match self.kind {
1132                 clean::TypeBindingKind::Equality { ref ty } => {
1133                     if f.alternate() {
1134                         write!(f, " = {:#}", ty.print())?;
1135                     } else {
1136                         write!(f, " = {}", ty.print())?;
1137                     }
1138                 }
1139                 clean::TypeBindingKind::Constraint { ref bounds } => {
1140                     if !bounds.is_empty() {
1141                         if f.alternate() {
1142                             write!(f, ": {:#}", print_generic_bounds(bounds))?;
1143                         } else {
1144                             write!(f, ":&nbsp;{}", print_generic_bounds(bounds))?;
1145                         }
1146                     }
1147                 }
1148             }
1149             Ok(())
1150         })
1151     }
1152 }
1153
1154 impl clean::Mutability {
1155     crate fn print_with_space(&self) -> &str {
1156         match self {
1157             clean::Immutable => "",
1158             clean::Mutable => "mut ",
1159         }
1160     }
1161 }
1162
1163 crate fn print_abi_with_space(abi: Abi) -> impl fmt::Display {
1164     display_fn(move |f| {
1165         let quot = if f.alternate() { "\"" } else { "&quot;" };
1166         match abi {
1167             Abi::Rust => Ok(()),
1168             abi => write!(f, "extern {0}{1}{0} ", quot, abi.name()),
1169         }
1170     })
1171 }
1172
1173 crate fn print_default_space<'a>(v: bool) -> &'a str {
1174     if v {
1175         "default "
1176     } else {
1177         ""
1178     }
1179 }
1180
1181 impl clean::GenericArg {
1182     crate fn print(&self) -> impl fmt::Display + '_ {
1183         display_fn(move |f| {
1184             match self {
1185                 clean::GenericArg::Lifetime(lt) => fmt::Display::fmt(&lt.print(), f),
1186                 clean::GenericArg::Type(ty) => fmt::Display::fmt(&ty.print(), f),
1187                 clean::GenericArg::Const(ct) => fmt::Display::fmt(&ct.print(), f),
1188             }
1189         })
1190     }
1191 }
1192
1193 crate fn display_fn(
1194     f: impl FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result,
1195 ) -> impl fmt::Display {
1196     WithFormatter(Cell::new(Some(f)))
1197 }
1198
1199 struct WithFormatter<F>(Cell<Option<F>>);
1200
1201 impl<F> fmt::Display for WithFormatter<F>
1202     where F: FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result,
1203 {
1204     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1205         (self.0.take()).unwrap()(f)
1206     }
1207 }