src/librustdoc/html/render/print_item.rs

   1 use clean::AttributesExt;
   2
   3 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
   4 use rustc_hir as hir;
   5 use rustc_hir::def::CtorKind;
   6 use rustc_hir::def_id::DefId;
   7 use rustc_middle::middle::stability;
   8 use rustc_middle::span_bug;
   9 use rustc_middle::ty::layout::LayoutError;
  10 use rustc_middle::ty::{self, Adt, TyCtxt};
  11 use rustc_span::hygiene::MacroKind;
  12 use rustc_span::symbol::{kw, sym, Symbol};
  13 use rustc_target::abi::{LayoutS, Primitive, TagEncoding, VariantIdx, Variants};
  14 use std::cmp::Ordering;
  15 use std::fmt;
  16 use std::rc::Rc;
  17
  18 use super::{
  19     collect_paths_for_type, document, ensure_trailing_slash, get_filtered_impls_for_reference,
  20     item_ty_to_section, notable_traits_button, notable_traits_json, render_all_impls,
  21     render_assoc_item, render_assoc_items, render_attributes_in_code, render_attributes_in_pre,
  22     render_impl, render_rightside, render_stability_since_raw,
  23     render_stability_since_raw_with_extra, AssocItemLink, Context, ImplRenderingParameters,
  24 };
  25 use crate::clean;
  26 use crate::config::ModuleSorting;
  27 use crate::formats::item_type::ItemType;
  28 use crate::formats::{AssocItemRender, Impl, RenderMode};
  29 use crate::html::escape::Escape;
  30 use crate::html::format::{
  31     join_with_double_colon, print_abi_with_space, print_constness_with_space, print_where_clause,
  32     visibility_print_with_space, Buffer, Ending, PrintWithSpace,
  33 };
  34 use crate::html::layout::Page;
  35 use crate::html::markdown::{HeadingOffset, MarkdownSummaryLine};
  36 use crate::html::url_parts_builder::UrlPartsBuilder;
  37 use crate::html::{highlight, static_files};
  38
  39 use askama::Template;
  40 use itertools::Itertools;
  41
  42 const ITEM_TABLE_OPEN: &str = "<div class=\"item-table\">";
  43 const ITEM_TABLE_CLOSE: &str = "</div>";
  44 const ITEM_TABLE_ROW_OPEN: &str = "<div class=\"item-row\">";
  45 const ITEM_TABLE_ROW_CLOSE: &str = "</div>";
  46
  47 // A component in a `use` path, like `string` in std::string::ToString
  48 struct PathComponent {
  49     path: String,
  50     name: Symbol,
  51 }
  52
  53 #[derive(Template)]
  54 #[template(path = "print_item.html")]
  55 struct ItemVars<'a> {
  56     static_root_path: &'a str,
  57     clipboard_svg: &'static static_files::StaticFile,
  58     typ: &'a str,
  59     name: &'a str,
  60     item_type: &'a str,
  61     path_components: Vec<PathComponent>,
  62     stability_since_raw: &'a str,
  63     src_href: Option<&'a str>,
  64 }
  65
  66 /// Calls `print_where_clause` and returns `true` if a `where` clause was generated.
  67 fn print_where_clause_and_check<'a, 'tcx: 'a>(
  68     buffer: &mut Buffer,
  69     gens: &'a clean::Generics,
  70     cx: &'a Context<'tcx>,
  71 ) -> bool {
  72     let len_before = buffer.len();
  73     write!(buffer, "{}", print_where_clause(gens, cx, 0, Ending::Newline));
  74     len_before != buffer.len()
  75 }
  76
  77 pub(super) fn print_item(
  78     cx: &mut Context<'_>,
  79     item: &clean::Item,
  80     buf: &mut Buffer,
  81     page: &Page<'_>,
  82 ) {
  83     debug_assert!(!item.is_stripped());
  84     let typ = match *item.kind {
  85         clean::ModuleItem(_) => {
  86             if item.is_crate() {
  87                 "Crate "
  88             } else {
  89                 "Module "
  90             }
  91         }
  92         clean::FunctionItem(..) | clean::ForeignFunctionItem(..) => "Function ",
  93         clean::TraitItem(..) => "Trait ",
  94         clean::StructItem(..) => "Struct ",
  95         clean::UnionItem(..) => "Union ",
  96         clean::EnumItem(..) => "Enum ",
  97         clean::TypedefItem(..) => "Type Definition ",
  98         clean::MacroItem(..) => "Macro ",
  99         clean::ProcMacroItem(ref mac) => match mac.kind {
 100             MacroKind::Bang => "Macro ",
 101             MacroKind::Attr => "Attribute Macro ",
 102             MacroKind::Derive => "Derive Macro ",
 103         },
 104         clean::PrimitiveItem(..) => "Primitive Type ",
 105         clean::StaticItem(..) | clean::ForeignStaticItem(..) => "Static ",
 106         clean::ConstantItem(..) => "Constant ",
 107         clean::ForeignTypeItem => "Foreign Type ",
 108         clean::KeywordItem => "Keyword ",
 109         clean::OpaqueTyItem(..) => "Opaque Type ",
 110         clean::TraitAliasItem(..) => "Trait Alias ",
 111         _ => {
 112             // We don't generate pages for any other type.
 113             unreachable!();
 114         }
 115     };
 116     let mut stability_since_raw = Buffer::new();
 117     render_stability_since_raw(
 118         &mut stability_since_raw,
 119         item.stable_since(cx.tcx()),
 120         item.const_stability(cx.tcx()),
 121         None,
 122         None,
 123     );
 124     let stability_since_raw: String = stability_since_raw.into_inner();
 125
 126     // Write source tag
 127     //
 128     // When this item is part of a `crate use` in a downstream crate, the
 129     // source link in the downstream documentation will actually come back to
 130     // this page, and this link will be auto-clicked. The `id` attribute is
 131     // used to find the link to auto-click.
 132     let src_href =
 133         if cx.include_sources && !item.is_primitive() { cx.src_href(item) } else { None };
 134
 135     let path_components = if item.is_primitive() || item.is_keyword() {
 136         vec![]
 137     } else {
 138         let cur = &cx.current;
 139         let amt = if item.is_mod() { cur.len() - 1 } else { cur.len() };
 140         cur.iter()
 141             .enumerate()
 142             .take(amt)
 143             .map(|(i, component)| PathComponent {
 144                 path: "../".repeat(cur.len() - i - 1),
 145                 name: *component,
 146             })
 147             .collect()
 148     };
 149
 150     let item_vars = ItemVars {
 151         static_root_path: &page.get_static_root_path(),
 152         clipboard_svg: &static_files::STATIC_FILES.clipboard_svg,
 153         typ,
 154         name: item.name.as_ref().unwrap().as_str(),
 155         item_type: &item.type_().to_string(),
 156         path_components,
 157         stability_since_raw: &stability_since_raw,
 158         src_href: src_href.as_deref(),
 159     };
 160
 161     item_vars.render_into(buf).unwrap();
 162
 163     match &*item.kind {
 164         clean::ModuleItem(ref m) => item_module(buf, cx, item, &m.items),
 165         clean::FunctionItem(ref f) | clean::ForeignFunctionItem(ref f) => {
 166             item_function(buf, cx, item, f)
 167         }
 168         clean::TraitItem(ref t) => item_trait(buf, cx, item, t),
 169         clean::StructItem(ref s) => item_struct(buf, cx, item, s),
 170         clean::UnionItem(ref s) => item_union(buf, cx, item, s),
 171         clean::EnumItem(ref e) => item_enum(buf, cx, item, e),
 172         clean::TypedefItem(ref t) => item_typedef(buf, cx, item, t),
 173         clean::MacroItem(ref m) => item_macro(buf, cx, item, m),
 174         clean::ProcMacroItem(ref m) => item_proc_macro(buf, cx, item, m),
 175         clean::PrimitiveItem(_) => item_primitive(buf, cx, item),
 176         clean::StaticItem(ref i) | clean::ForeignStaticItem(ref i) => item_static(buf, cx, item, i),
 177         clean::ConstantItem(ref c) => item_constant(buf, cx, item, c),
 178         clean::ForeignTypeItem => item_foreign_type(buf, cx, item),
 179         clean::KeywordItem => item_keyword(buf, cx, item),
 180         clean::OpaqueTyItem(ref e) => item_opaque_ty(buf, cx, item, e),
 181         clean::TraitAliasItem(ref ta) => item_trait_alias(buf, cx, item, ta),
 182         _ => {
 183             // We don't generate pages for any other type.
 184             unreachable!();
 185         }
 186     }
 187
 188     // Render notable-traits.js used for all methods in this module.
 189     if !cx.types_with_notable_traits.is_empty() {
 190         write!(
 191             buf,
 192             r#"<script type="text/json" id="notable-traits-data">{}</script>"#,
 193             notable_traits_json(cx.types_with_notable_traits.iter(), cx)
 194         );
 195         cx.types_with_notable_traits.clear();
 196     }
 197 }
 198
 199 /// For large structs, enums, unions, etc, determine whether to hide their fields
 200 fn should_hide_fields(n_fields: usize) -> bool {
 201     n_fields > 12
 202 }
 203
 204 fn toggle_open(w: &mut Buffer, text: impl fmt::Display) {
 205     write!(
 206         w,
 207         "<details class=\"rustdoc-toggle type-contents-toggle\">\
 208             <summary class=\"hideme\">\
 209                 <span>Show {}</span>\
 210             </summary>",
 211         text
 212     );
 213 }
 214
 215 fn toggle_close(w: &mut Buffer) {
 216     w.write_str("</details>");
 217 }
 218
 219 fn item_module(w: &mut Buffer, cx: &mut Context<'_>, item: &clean::Item, items: &[clean::Item]) {
 220     document(w, cx, item, None, HeadingOffset::H2);
 221
 222     let mut indices = (0..items.len()).filter(|i| !items[*i].is_stripped()).collect::<Vec<usize>>();
 223
 224     // the order of item types in the listing
 225     fn reorder(ty: ItemType) -> u8 {
 226         match ty {
 227             ItemType::ExternCrate => 0,
 228             ItemType::Import => 1,
 229             ItemType::Primitive => 2,
 230             ItemType::Module => 3,
 231             ItemType::Macro => 4,
 232             ItemType::Struct => 5,
 233             ItemType::Enum => 6,
 234             ItemType::Constant => 7,
 235             ItemType::Static => 8,
 236             ItemType::Trait => 9,
 237             ItemType::Function => 10,
 238             ItemType::Typedef => 12,
 239             ItemType::Union => 13,
 240             _ => 14 + ty as u8,
 241         }
 242     }
 243
 244     fn cmp(
 245         i1: &clean::Item,
 246         i2: &clean::Item,
 247         idx1: usize,
 248         idx2: usize,
 249         tcx: TyCtxt<'_>,
 250     ) -> Ordering {
 251         let ty1 = i1.type_();
 252         let ty2 = i2.type_();
 253         if item_ty_to_section(ty1) != item_ty_to_section(ty2)
 254             || (ty1 != ty2 && (ty1 == ItemType::ExternCrate || ty2 == ItemType::ExternCrate))
 255         {
 256             return (reorder(ty1), idx1).cmp(&(reorder(ty2), idx2));
 257         }
 258         let s1 = i1.stability(tcx).as_ref().map(|s| s.level);
 259         let s2 = i2.stability(tcx).as_ref().map(|s| s.level);
 260         if let (Some(a), Some(b)) = (s1, s2) {
 261             match (a.is_stable(), b.is_stable()) {
 262                 (true, true) | (false, false) => {}
 263                 (false, true) => return Ordering::Less,
 264                 (true, false) => return Ordering::Greater,
 265             }
 266         }
 267         let lhs = i1.name.unwrap_or(kw::Empty);
 268         let rhs = i2.name.unwrap_or(kw::Empty);
 269         compare_names(lhs.as_str(), rhs.as_str())
 270     }
 271
 272     match cx.shared.module_sorting {
 273         ModuleSorting::Alphabetical => {
 274             indices.sort_by(|&i1, &i2| cmp(&items[i1], &items[i2], i1, i2, cx.tcx()));
 275         }
 276         ModuleSorting::DeclarationOrder => {}
 277     }
 278     // This call is to remove re-export duplicates in cases such as:
 279     //
 280     // ```
 281     // pub(crate) mod foo {
 282     //     pub(crate) mod bar {
 283     //         pub(crate) trait Double { fn foo(); }
 284     //     }
 285     // }
 286     //
 287     // pub(crate) use foo::bar::*;
 288     // pub(crate) use foo::*;
 289     // ```
 290     //
 291     // `Double` will appear twice in the generated docs.
 292     //
 293     // FIXME: This code is quite ugly and could be improved. Small issue: DefId
 294     // can be identical even if the elements are different (mostly in imports).
 295     // So in case this is an import, we keep everything by adding a "unique id"
 296     // (which is the position in the vector).
 297     indices.dedup_by_key(|i| {
 298         (
 299             items[*i].item_id,
 300             if items[*i].name.is_some() { Some(full_path(cx, &items[*i])) } else { None },
 301             items[*i].type_(),
 302             if items[*i].is_import() { *i } else { 0 },
 303         )
 304     });
 305
 306     debug!("{:?}", indices);
 307     let mut last_section = None;
 308
 309     for &idx in &indices {
 310         let myitem = &items[idx];
 311         if myitem.is_stripped() {
 312             continue;
 313         }
 314
 315         let my_section = item_ty_to_section(myitem.type_());
 316         if Some(my_section) != last_section {
 317             if last_section.is_some() {
 318                 w.write_str(ITEM_TABLE_CLOSE);
 319             }
 320             last_section = Some(my_section);
 321             write!(
 322                 w,
 323                 "<h2 id=\"{id}\" class=\"small-section-header\">\
 324                     <a href=\"#{id}\">{name}</a>\
 325                  </h2>{}",
 326                 ITEM_TABLE_OPEN,
 327                 id = cx.derive_id(my_section.id().to_owned()),
 328                 name = my_section.name(),
 329             );
 330         }
 331
 332         let tcx = cx.tcx();
 333         match *myitem.kind {
 334             clean::ExternCrateItem { ref src } => {
 335                 use crate::html::format::anchor;
 336
 337                 w.write_str(ITEM_TABLE_ROW_OPEN);
 338                 match *src {
 339                     Some(src) => write!(
 340                         w,
 341                         "<div class=\"item-left\"><code>{}extern crate {} as {};",
 342                         visibility_print_with_space(myitem.visibility(tcx), myitem.item_id, cx),
 343                         anchor(myitem.item_id.expect_def_id(), src, cx),
 344                         myitem.name.unwrap(),
 345                     ),
 346                     None => write!(
 347                         w,
 348                         "<div class=\"item-left\"><code>{}extern crate {};",
 349                         visibility_print_with_space(myitem.visibility(tcx), myitem.item_id, cx),
 350                         anchor(myitem.item_id.expect_def_id(), myitem.name.unwrap(), cx),
 351                     ),
 352                 }
 353                 w.write_str("</code></div>");
 354                 w.write_str(ITEM_TABLE_ROW_CLOSE);
 355             }
 356
 357             clean::ImportItem(ref import) => {
 358                 let (stab, stab_tags) = if let Some(import_def_id) = import.source.did {
 359                     let ast_attrs = cx.tcx().get_attrs_unchecked(import_def_id);
 360                     let import_attrs = Box::new(clean::Attributes::from_ast(ast_attrs));
 361
 362                     // Just need an item with the correct def_id and attrs
 363                     let import_item = clean::Item {
 364                         item_id: import_def_id.into(),
 365                         attrs: import_attrs,
 366                         cfg: ast_attrs.cfg(cx.tcx(), &cx.cache().hidden_cfg),
 367                         ..myitem.clone()
 368                     };
 369
 370                     let stab = import_item.stability_class(cx.tcx());
 371                     let stab_tags = Some(extra_info_tags(&import_item, item, cx.tcx()));
 372                     (stab, stab_tags)
 373                 } else {
 374                     (None, None)
 375                 };
 376
 377                 let add = if stab.is_some() { " " } else { "" };
 378
 379                 w.write_str(ITEM_TABLE_ROW_OPEN);
 380                 let id = match import.kind {
 381                     clean::ImportKind::Simple(s) => {
 382                         format!(" id=\"{}\"", cx.derive_id(format!("reexport.{}", s)))
 383                     }
 384                     clean::ImportKind::Glob => String::new(),
 385                 };
 386                 let stab_tags = stab_tags.unwrap_or_default();
 387                 let (stab_tags_before, stab_tags_after) = if stab_tags.is_empty() {
 388                     ("", "")
 389                 } else {
 390                     ("<div class=\"item-right docblock-short\">", "</div>")
 391                 };
 392                 write!(
 393                     w,
 394                     "<div class=\"item-left {stab}{add}import-item\"{id}>\
 395                          <code>{vis}{imp}</code>\
 396                      </div>\
 397                      {stab_tags_before}{stab_tags}{stab_tags_after}",
 398                     stab = stab.unwrap_or_default(),
 399                     vis = visibility_print_with_space(myitem.visibility(tcx), myitem.item_id, cx),
 400                     imp = import.print(cx),
 401                 );
 402                 w.write_str(ITEM_TABLE_ROW_CLOSE);
 403             }
 404
 405             _ => {
 406                 if myitem.name.is_none() {
 407                     continue;
 408                 }
 409
 410                 let unsafety_flag = match *myitem.kind {
 411                     clean::FunctionItem(_) | clean::ForeignFunctionItem(_)
 412                         if myitem.fn_header(cx.tcx()).unwrap().unsafety
 413                             == hir::Unsafety::Unsafe =>
 414                     {
 415                         "<sup title=\"unsafe function\">⚠</sup>"
 416                     }
 417                     _ => "",
 418                 };
 419
 420                 let stab = myitem.stability_class(cx.tcx());
 421                 let add = if stab.is_some() { " " } else { "" };
 422
 423                 let visibility_emoji = match myitem.visibility(tcx) {
 424                     Some(ty::Visibility::Restricted(_)) => {
 425                         "<span title=\"Restricted Visibility\">&nbsp;🔒</span> "
 426                     }
 427                     _ => "",
 428                 };
 429
 430                 let doc_value = myitem.doc_value().unwrap_or_default();
 431                 w.write_str(ITEM_TABLE_ROW_OPEN);
 432                 let docs = MarkdownSummaryLine(&doc_value, &myitem.links(cx)).into_string();
 433                 let (docs_before, docs_after) = if docs.is_empty() {
 434                     ("", "")
 435                 } else {
 436                     ("<div class=\"item-right docblock-short\">", "</div>")
 437                 };
 438                 write!(
 439                     w,
 440                     "<div class=\"item-left {stab}{add}module-item\">\
 441                         <a class=\"{class}\" href=\"{href}\" title=\"{title}\">{name}</a>\
 442                         {visibility_emoji}\
 443                         {unsafety_flag}\
 444                         {stab_tags}\
 445                      </div>\
 446                      {docs_before}{docs}{docs_after}",
 447                     name = myitem.name.unwrap(),
 448                     visibility_emoji = visibility_emoji,
 449                     stab_tags = extra_info_tags(myitem, item, cx.tcx()),
 450                     class = myitem.type_(),
 451                     add = add,
 452                     stab = stab.unwrap_or_default(),
 453                     unsafety_flag = unsafety_flag,
 454                     href = item_path(myitem.type_(), myitem.name.unwrap().as_str()),
 455                     title = [full_path(cx, myitem), myitem.type_().to_string()]
 456                         .iter()
 457                         .filter_map(|s| if !s.is_empty() { Some(s.as_str()) } else { None })
 458                         .collect::<Vec<_>>()
 459                         .join(" "),
 460                 );
 461                 w.write_str(ITEM_TABLE_ROW_CLOSE);
 462             }
 463         }
 464     }
 465
 466     if last_section.is_some() {
 467         w.write_str(ITEM_TABLE_CLOSE);
 468     }
 469 }
 470
 471 /// Render the stability, deprecation and portability tags that are displayed in the item's summary
 472 /// at the module level.
 473 fn extra_info_tags(item: &clean::Item, parent: &clean::Item, tcx: TyCtxt<'_>) -> String {
 474     let mut tags = String::new();
 475
 476     fn tag_html(class: &str, title: &str, contents: &str) -> String {
 477         format!(r#"<span class="stab {}" title="{}">{}</span>"#, class, Escape(title), contents)
 478     }
 479
 480     // The trailing space after each tag is to space it properly against the rest of the docs.
 481     if let Some(depr) = &item.deprecation(tcx) {
 482         let mut message = "Deprecated";
 483         if !stability::deprecation_in_effect(depr) {
 484             message = "Deprecation planned";
 485         }
 486         tags += &tag_html("deprecated", "", message);
 487     }
 488
 489     // The "rustc_private" crates are permanently unstable so it makes no sense
 490     // to render "unstable" everywhere.
 491     if item.stability(tcx).as_ref().map(|s| s.is_unstable() && s.feature != sym::rustc_private)
 492         == Some(true)
 493     {
 494         tags += &tag_html("unstable", "", "Experimental");
 495     }
 496
 497     let cfg = match (&item.cfg, parent.cfg.as_ref()) {
 498         (Some(cfg), Some(parent_cfg)) => cfg.simplify_with(parent_cfg),
 499         (cfg, _) => cfg.as_deref().cloned(),
 500     };
 501
 502     debug!("Portability name={:?} {:?} - {:?} = {:?}", item.name, item.cfg, parent.cfg, cfg);
 503     if let Some(ref cfg) = cfg {
 504         tags += &tag_html("portability", &cfg.render_long_plain(), &cfg.render_short_html());
 505     }
 506
 507     tags
 508 }
 509
 510 fn item_function(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, f: &clean::Function) {
 511     let tcx = cx.tcx();
 512     let header = it.fn_header(tcx).expect("printing a function which isn't a function");
 513     let constness = print_constness_with_space(&header.constness, it.const_stability(tcx));
 514     let unsafety = header.unsafety.print_with_space();
 515     let abi = print_abi_with_space(header.abi).to_string();
 516     let asyncness = header.asyncness.print_with_space();
 517     let visibility = visibility_print_with_space(it.visibility(tcx), it.item_id, cx).to_string();
 518     let name = it.name.unwrap();
 519
 520     let generics_len = format!("{:#}", f.generics.print(cx)).len();
 521     let header_len = "fn ".len()
 522         + visibility.len()
 523         + constness.len()
 524         + asyncness.len()
 525         + unsafety.len()
 526         + abi.len()
 527         + name.as_str().len()
 528         + generics_len;
 529
 530     let notable_traits =
 531         f.decl.output.as_return().and_then(|output| notable_traits_button(output, cx));
 532
 533     wrap_into_item_decl(w, |w| {
 534         wrap_item(w, "fn", |w| {
 535             render_attributes_in_pre(w, it, "");
 536             w.reserve(header_len);
 537             write!(
 538                 w,
 539                 "{vis}{constness}{asyncness}{unsafety}{abi}fn \
 540                  {name}{generics}{decl}{notable_traits}{where_clause}",
 541                 vis = visibility,
 542                 constness = constness,
 543                 asyncness = asyncness,
 544                 unsafety = unsafety,
 545                 abi = abi,
 546                 name = name,
 547                 generics = f.generics.print(cx),
 548                 where_clause = print_where_clause(&f.generics, cx, 0, Ending::Newline),
 549                 decl = f.decl.full_print(header_len, 0, cx),
 550                 notable_traits = notable_traits.unwrap_or_default(),
 551             );
 552         });
 553     });
 554     document(w, cx, it, None, HeadingOffset::H2);
 555 }
 556
 557 fn item_trait(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, t: &clean::Trait) {
 558     let tcx = cx.tcx();
 559     let bounds = bounds(&t.bounds, false, cx);
 560     let required_types = t.items.iter().filter(|m| m.is_ty_associated_type()).collect::<Vec<_>>();
 561     let provided_types = t.items.iter().filter(|m| m.is_associated_type()).collect::<Vec<_>>();
 562     let required_consts = t.items.iter().filter(|m| m.is_ty_associated_const()).collect::<Vec<_>>();
 563     let provided_consts = t.items.iter().filter(|m| m.is_associated_const()).collect::<Vec<_>>();
 564     let required_methods = t.items.iter().filter(|m| m.is_ty_method()).collect::<Vec<_>>();
 565     let provided_methods = t.items.iter().filter(|m| m.is_method()).collect::<Vec<_>>();
 566     let count_types = required_types.len() + provided_types.len();
 567     let count_consts = required_consts.len() + provided_consts.len();
 568     let count_methods = required_methods.len() + provided_methods.len();
 569     let must_implement_one_of_functions = tcx.trait_def(t.def_id).must_implement_one_of.clone();
 570
 571     // Output the trait definition
 572     wrap_into_item_decl(w, |w| {
 573         wrap_item(w, "trait", |w| {
 574             render_attributes_in_pre(w, it, "");
 575             write!(
 576                 w,
 577                 "{}{}{}trait {}{}{}",
 578                 visibility_print_with_space(it.visibility(tcx), it.item_id, cx),
 579                 t.unsafety(tcx).print_with_space(),
 580                 if t.is_auto(tcx) { "auto " } else { "" },
 581                 it.name.unwrap(),
 582                 t.generics.print(cx),
 583                 bounds
 584             );
 585
 586             if !t.generics.where_predicates.is_empty() {
 587                 write!(w, "{}", print_where_clause(&t.generics, cx, 0, Ending::Newline));
 588             } else {
 589                 w.write_str(" ");
 590             }
 591
 592             if t.items.is_empty() {
 593                 w.write_str("{ }");
 594             } else {
 595                 // FIXME: we should be using a derived_id for the Anchors here
 596                 w.write_str("{\n");
 597                 let mut toggle = false;
 598
 599                 // If there are too many associated types, hide _everything_
 600                 if should_hide_fields(count_types) {
 601                     toggle = true;
 602                     toggle_open(
 603                         w,
 604                         format_args!(
 605                             "{} associated items",
 606                             count_types + count_consts + count_methods
 607                         ),
 608                     );
 609                 }
 610                 for types in [&required_types, &provided_types] {
 611                     for t in types {
 612                         render_assoc_item(
 613                             w,
 614                             t,
 615                             AssocItemLink::Anchor(None),
 616                             ItemType::Trait,
 617                             cx,
 618                             RenderMode::Normal,
 619                         );
 620                         w.write_str(";\n");
 621                     }
 622                 }
 623                 // If there are too many associated constants, hide everything after them
 624                 // We also do this if the types + consts is large because otherwise we could
 625                 // render a bunch of types and _then_ a bunch of consts just because both were
 626                 // _just_ under the limit
 627                 if !toggle && should_hide_fields(count_types + count_consts) {
 628                     toggle = true;
 629                     toggle_open(
 630                         w,
 631                         format_args!(
 632                             "{} associated constant{} and {} method{}",
 633                             count_consts,
 634                             pluralize(count_consts),
 635                             count_methods,
 636                             pluralize(count_methods),
 637                         ),
 638                     );
 639                 }
 640                 if count_types != 0 && (count_consts != 0 || count_methods != 0) {
 641                     w.write_str("\n");
 642                 }
 643                 for consts in [&required_consts, &provided_consts] {
 644                     for c in consts {
 645                         render_assoc_item(
 646                             w,
 647                             c,
 648                             AssocItemLink::Anchor(None),
 649                             ItemType::Trait,
 650                             cx,
 651                             RenderMode::Normal,
 652                         );
 653                         w.write_str(";\n");
 654                     }
 655                 }
 656                 if !toggle && should_hide_fields(count_methods) {
 657                     toggle = true;
 658                     toggle_open(w, format_args!("{} methods", count_methods));
 659                 }
 660                 if count_consts != 0 && count_methods != 0 {
 661                     w.write_str("\n");
 662                 }
 663                 for (pos, m) in required_methods.iter().enumerate() {
 664                     render_assoc_item(
 665                         w,
 666                         m,
 667                         AssocItemLink::Anchor(None),
 668                         ItemType::Trait,
 669                         cx,
 670                         RenderMode::Normal,
 671                     );
 672                     w.write_str(";\n");
 673
 674                     if pos < required_methods.len() - 1 {
 675                         w.write_str("<span class=\"item-spacer\"></span>");
 676                     }
 677                 }
 678                 if !required_methods.is_empty() && !provided_methods.is_empty() {
 679                     w.write_str("\n");
 680                 }
 681                 for (pos, m) in provided_methods.iter().enumerate() {
 682                     render_assoc_item(
 683                         w,
 684                         m,
 685                         AssocItemLink::Anchor(None),
 686                         ItemType::Trait,
 687                         cx,
 688                         RenderMode::Normal,
 689                     );
 690                     match *m.kind {
 691                         clean::MethodItem(ref inner, _)
 692                             if !inner.generics.where_predicates.is_empty() =>
 693                         {
 694                             w.write_str(",\n    { ... }\n");
 695                         }
 696                         _ => {
 697                             w.write_str(" { ... }\n");
 698                         }
 699                     }
 700
 701                     if pos < provided_methods.len() - 1 {
 702                         w.write_str("<span class=\"item-spacer\"></span>");
 703                     }
 704                 }
 705                 if toggle {
 706                     toggle_close(w);
 707                 }
 708                 w.write_str("}");
 709             }
 710         });
 711     });
 712
 713     // Trait documentation
 714     document(w, cx, it, None, HeadingOffset::H2);
 715
 716     fn write_small_section_header(w: &mut Buffer, id: &str, title: &str, extra_content: &str) {
 717         write!(
 718             w,
 719             "<h2 id=\"{0}\" class=\"small-section-header\">\
 720                 {1}<a href=\"#{0}\" class=\"anchor\">§</a>\
 721              </h2>{2}",
 722             id, title, extra_content
 723         )
 724     }
 725
 726     fn trait_item(w: &mut Buffer, cx: &mut Context<'_>, m: &clean::Item, t: &clean::Item) {
 727         let name = m.name.unwrap();
 728         info!("Documenting {} on {:?}", name, t.name);
 729         let item_type = m.type_();
 730         let id = cx.derive_id(format!("{}.{}", item_type, name));
 731         let mut content = Buffer::empty_from(w);
 732         document(&mut content, cx, m, Some(t), HeadingOffset::H5);
 733         let toggled = !content.is_empty();
 734         if toggled {
 735             write!(w, "<details class=\"rustdoc-toggle method-toggle\" open><summary>");
 736         }
 737         write!(w, "<section id=\"{}\" class=\"method has-srclink\">", id);
 738         render_rightside(w, cx, m, t, RenderMode::Normal);
 739         write!(w, "<h4 class=\"code-header\">");
 740         render_assoc_item(
 741             w,
 742             m,
 743             AssocItemLink::Anchor(Some(&id)),
 744             ItemType::Impl,
 745             cx,
 746             RenderMode::Normal,
 747         );
 748         w.write_str("</h4>");
 749         w.write_str("</section>");
 750         if toggled {
 751             write!(w, "</summary>");
 752             w.push_buffer(content);
 753             write!(w, "</details>");
 754         }
 755     }
 756
 757     if !required_types.is_empty() {
 758         write_small_section_header(
 759             w,
 760             "required-associated-types",
 761             "Required Associated Types",
 762             "<div class=\"methods\">",
 763         );
 764         for t in required_types {
 765             trait_item(w, cx, t, it);
 766         }
 767         w.write_str("</div>");
 768     }
 769     if !provided_types.is_empty() {
 770         write_small_section_header(
 771             w,
 772             "provided-associated-types",
 773             "Provided Associated Types",
 774             "<div class=\"methods\">",
 775         );
 776         for t in provided_types {
 777             trait_item(w, cx, t, it);
 778         }
 779         w.write_str("</div>");
 780     }
 781
 782     if !required_consts.is_empty() {
 783         write_small_section_header(
 784             w,
 785             "required-associated-consts",
 786             "Required Associated Constants",
 787             "<div class=\"methods\">",
 788         );
 789         for t in required_consts {
 790             trait_item(w, cx, t, it);
 791         }
 792         w.write_str("</div>");
 793     }
 794     if !provided_consts.is_empty() {
 795         write_small_section_header(
 796             w,
 797             "provided-associated-consts",
 798             "Provided Associated Constants",
 799             "<div class=\"methods\">",
 800         );
 801         for t in provided_consts {
 802             trait_item(w, cx, t, it);
 803         }
 804         w.write_str("</div>");
 805     }
 806
 807     // Output the documentation for each function individually
 808     if !required_methods.is_empty() || must_implement_one_of_functions.is_some() {
 809         write_small_section_header(
 810             w,
 811             "required-methods",
 812             "Required Methods",
 813             "<div class=\"methods\">",
 814         );
 815
 816         if let Some(list) = must_implement_one_of_functions.as_deref() {
 817             write!(
 818                 w,
 819                 "<div class=\"stab must_implement\">At least one of the `{}` methods is required.</div>",
 820                 list.iter().join("`, `")
 821             );
 822         }
 823
 824         for m in required_methods {
 825             trait_item(w, cx, m, it);
 826         }
 827         w.write_str("</div>");
 828     }
 829     if !provided_methods.is_empty() {
 830         write_small_section_header(
 831             w,
 832             "provided-methods",
 833             "Provided Methods",
 834             "<div class=\"methods\">",
 835         );
 836         for m in provided_methods {
 837             trait_item(w, cx, m, it);
 838         }
 839         w.write_str("</div>");
 840     }
 841
 842     // If there are methods directly on this trait object, render them here.
 843     render_assoc_items(w, cx, it, it.item_id.expect_def_id(), AssocItemRender::All);
 844
 845     let cloned_shared = Rc::clone(&cx.shared);
 846     let cache = &cloned_shared.cache;
 847     let mut extern_crates = FxHashSet::default();
 848     if let Some(implementors) = cache.implementors.get(&it.item_id.expect_def_id()) {
 849         // The DefId is for the first Type found with that name. The bool is
 850         // if any Types with the same name but different DefId have been found.
 851         let mut implementor_dups: FxHashMap<Symbol, (DefId, bool)> = FxHashMap::default();
 852         for implementor in implementors {
 853             if let Some(did) = implementor.inner_impl().for_.without_borrowed_ref().def_id(cache) &&
 854                 !did.is_local() {
 855                 extern_crates.insert(did.krate);
 856             }
 857             match implementor.inner_impl().for_.without_borrowed_ref() {
 858                 clean::Type::Path { ref path } if !path.is_assoc_ty() => {
 859                     let did = path.def_id();
 860                     let &mut (prev_did, ref mut has_duplicates) =
 861                         implementor_dups.entry(path.last()).or_insert((did, false));
 862                     if prev_did != did {
 863                         *has_duplicates = true;
 864                     }
 865                 }
 866                 _ => {}
 867             }
 868         }
 869
 870         let (local, foreign) =
 871             implementors.iter().partition::<Vec<_>, _>(|i| i.is_on_local_type(cx));
 872
 873         let (mut synthetic, mut concrete): (Vec<&&Impl>, Vec<&&Impl>) =
 874             local.iter().partition(|i| i.inner_impl().kind.is_auto());
 875
 876         synthetic.sort_by(|a, b| compare_impl(a, b, cx));
 877         concrete.sort_by(|a, b| compare_impl(a, b, cx));
 878
 879         if !foreign.is_empty() {
 880             write_small_section_header(w, "foreign-impls", "Implementations on Foreign Types", "");
 881
 882             for implementor in foreign {
 883                 let provided_methods = implementor.inner_impl().provided_trait_methods(cx.tcx());
 884                 let assoc_link =
 885                     AssocItemLink::GotoSource(implementor.impl_item.item_id, &provided_methods);
 886                 render_impl(
 887                     w,
 888                     cx,
 889                     implementor,
 890                     it,
 891                     assoc_link,
 892                     RenderMode::Normal,
 893                     None,
 894                     &[],
 895                     ImplRenderingParameters {
 896                         show_def_docs: false,
 897                         show_default_items: false,
 898                         show_non_assoc_items: true,
 899                         toggle_open_by_default: false,
 900                     },
 901                 );
 902             }
 903         }
 904
 905         write_small_section_header(
 906             w,
 907             "implementors",
 908             "Implementors",
 909             "<div id=\"implementors-list\">",
 910         );
 911         for implementor in concrete {
 912             render_implementor(cx, implementor, it, w, &implementor_dups, &[]);
 913         }
 914         w.write_str("</div>");
 915
 916         if t.is_auto(cx.tcx()) {
 917             write_small_section_header(
 918                 w,
 919                 "synthetic-implementors",
 920                 "Auto implementors",
 921                 "<div id=\"synthetic-implementors-list\">",
 922             );
 923             for implementor in synthetic {
 924                 render_implementor(
 925                     cx,
 926                     implementor,
 927                     it,
 928                     w,
 929                     &implementor_dups,
 930                     &collect_paths_for_type(implementor.inner_impl().for_.clone(), cache),
 931                 );
 932             }
 933             w.write_str("</div>");
 934         }
 935     } else {
 936         // even without any implementations to write in, we still want the heading and list, so the
 937         // implementors javascript file pulled in below has somewhere to write the impls into
 938         write_small_section_header(
 939             w,
 940             "implementors",
 941             "Implementors",
 942             "<div id=\"implementors-list\"></div>",
 943         );
 944
 945         if t.is_auto(cx.tcx()) {
 946             write_small_section_header(
 947                 w,
 948                 "synthetic-implementors",
 949                 "Auto implementors",
 950                 "<div id=\"synthetic-implementors-list\"></div>",
 951             );
 952         }
 953     }
 954
 955     // Include implementors in crates that depend on the current crate.
 956     //
 957     // This is complicated by the way rustdoc is invoked, which is basically
 958     // the same way rustc is invoked: it gets called, one at a time, for each
 959     // crate. When building the rustdocs for the current crate, rustdoc can
 960     // see crate metadata for its dependencies, but cannot see metadata for its
 961     // dependents.
 962     //
 963     // To make this work, we generate a "hook" at this stage, and our
 964     // dependents can "plug in" to it when they build. For simplicity's sake,
 965     // it's [JSONP]: a JavaScript file with the data we need (and can parse),
 966     // surrounded by a tiny wrapper that the Rust side ignores, but allows the
 967     // JavaScript side to include without having to worry about Same Origin
 968     // Policy. The code for *that* is in `write_shared.rs`.
 969     //
 970     // This is further complicated by `#[doc(inline)]`. We want all copies
 971     // of an inlined trait to reference the same JS file, to address complex
 972     // dependency graphs like this one (lower crates depend on higher crates):
 973     //
 974     // ```text
 975     //  --------------------------------------------
 976     //  |            crate A: trait Foo            |
 977     //  --------------------------------------------
 978     //      |                               |
 979     //  --------------------------------    |
 980     //  | crate B: impl A::Foo for Bar |    |
 981     //  --------------------------------    |
 982     //      |                               |
 983     //  ---------------------------------------------
 984     //  | crate C: #[doc(inline)] use A::Foo as Baz |
 985     //  |          impl Baz for Quux                |
 986     //  ---------------------------------------------
 987     // ```
 988     //
 989     // Basically, we want `C::Baz` and `A::Foo` to show the same set of
 990     // impls, which is easier if they both treat `/implementors/A/trait.Foo.js`
 991     // as the Single Source of Truth.
 992     //
 993     // We also want the `impl Baz for Quux` to be written to
 994     // `trait.Foo.js`. However, when we generate plain HTML for `C::Baz`,
 995     // we're going to want to generate plain HTML for `impl Baz for Quux` too,
 996     // because that'll load faster, and it's better for SEO. And we don't want
 997     // the same impl to show up twice on the same page.
 998     //
 999     // To make this work, the implementors JS file has a structure kinda
1000     // like this:
1001     //
1002     // ```js
1003     // JSONP({
1004     // "B": {"impl A::Foo for Bar"},
1005     // "C": {"impl Baz for Quux"},
1006     // });
1007     // ```
1008     //
1009     // First of all, this means we can rebuild a crate, and it'll replace its own
1010     // data if something changes. That is, `rustdoc` is idempotent. The other
1011     // advantage is that we can list the crates that get included in the HTML,
1012     // and ignore them when doing the JavaScript-based part of rendering.
1013     // So C's HTML will have something like this:
1014     //
1015     // ```html
1016     // <script src="/implementors/A/trait.Foo.js"
1017     //     data-ignore-extern-crates="A,B" async></script>
1018     // ```
1019     //
1020     // And, when the JS runs, anything in data-ignore-extern-crates is known
1021     // to already be in the HTML, and will be ignored.
1022     //
1023     // [JSONP]: https://en.wikipedia.org/wiki/JSONP
1024     let mut js_src_path: UrlPartsBuilder = std::iter::repeat("..")
1025         .take(cx.current.len())
1026         .chain(std::iter::once("implementors"))
1027         .collect();
1028     if let Some(did) = it.item_id.as_def_id() &&
1029         let get_extern = { || cache.external_paths.get(&did).map(|s| s.0.clone()) } &&
1030         let Some(fqp) = cache.exact_paths.get(&did).cloned().or_else(get_extern) {
1031         js_src_path.extend(fqp[..fqp.len() - 1].iter().copied());
1032         js_src_path.push_fmt(format_args!("{}.{}.js", it.type_(), fqp.last().unwrap()));
1033     } else {
1034         js_src_path.extend(cx.current.iter().copied());
1035         js_src_path.push_fmt(format_args!("{}.{}.js", it.type_(), it.name.unwrap()));
1036     }
1037     let extern_crates = extern_crates
1038         .into_iter()
1039         .map(|cnum| tcx.crate_name(cnum).to_string())
1040         .collect::<Vec<_>>()
1041         .join(",");
1042     let (extern_before, extern_after) =
1043         if extern_crates.is_empty() { ("", "") } else { (" data-ignore-extern-crates=\"", "\"") };
1044     write!(
1045         w,
1046         "<script src=\"{src}\"{extern_before}{extern_crates}{extern_after} async></script>",
1047         src = js_src_path.finish(),
1048     );
1049 }
1050
1051 fn item_trait_alias(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, t: &clean::TraitAlias) {
1052     wrap_into_item_decl(w, |w| {
1053         wrap_item(w, "trait-alias", |w| {
1054             render_attributes_in_pre(w, it, "");
1055             write!(
1056                 w,
1057                 "trait {}{}{} = {};",
1058                 it.name.unwrap(),
1059                 t.generics.print(cx),
1060                 print_where_clause(&t.generics, cx, 0, Ending::Newline),
1061                 bounds(&t.bounds, true, cx)
1062             );
1063         });
1064     });
1065
1066     document(w, cx, it, None, HeadingOffset::H2);
1067
1068     // Render any items associated directly to this alias, as otherwise they
1069     // won't be visible anywhere in the docs. It would be nice to also show
1070     // associated items from the aliased type (see discussion in #32077), but
1071     // we need #14072 to make sense of the generics.
1072     render_assoc_items(w, cx, it, it.item_id.expect_def_id(), AssocItemRender::All)
1073 }
1074
1075 fn item_opaque_ty(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, t: &clean::OpaqueTy) {
1076     wrap_into_item_decl(w, |w| {
1077         wrap_item(w, "opaque", |w| {
1078             render_attributes_in_pre(w, it, "");
1079             write!(
1080                 w,
1081                 "type {}{}{where_clause} = impl {bounds};",
1082                 it.name.unwrap(),
1083                 t.generics.print(cx),
1084                 where_clause = print_where_clause(&t.generics, cx, 0, Ending::Newline),
1085                 bounds = bounds(&t.bounds, false, cx),
1086             );
1087         });
1088     });
1089
1090     document(w, cx, it, None, HeadingOffset::H2);
1091
1092     // Render any items associated directly to this alias, as otherwise they
1093     // won't be visible anywhere in the docs. It would be nice to also show
1094     // associated items from the aliased type (see discussion in #32077), but
1095     // we need #14072 to make sense of the generics.
1096     render_assoc_items(w, cx, it, it.item_id.expect_def_id(), AssocItemRender::All)
1097 }
1098
1099 fn item_typedef(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, t: &clean::Typedef) {
1100     fn write_content(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::Typedef) {
1101         wrap_item(w, "typedef", |w| {
1102             render_attributes_in_pre(w, it, "");
1103             write!(w, "{}", visibility_print_with_space(it.visibility(cx.tcx()), it.item_id, cx));
1104             write!(
1105                 w,
1106                 "type {}{}{where_clause} = {type_};",
1107                 it.name.unwrap(),
1108                 t.generics.print(cx),
1109                 where_clause = print_where_clause(&t.generics, cx, 0, Ending::Newline),
1110                 type_ = t.type_.print(cx),
1111             );
1112         });
1113     }
1114
1115     wrap_into_item_decl(w, |w| write_content(w, cx, it, t));
1116
1117     document(w, cx, it, None, HeadingOffset::H2);
1118
1119     let def_id = it.item_id.expect_def_id();
1120     // Render any items associated directly to this alias, as otherwise they
1121     // won't be visible anywhere in the docs. It would be nice to also show
1122     // associated items from the aliased type (see discussion in #32077), but
1123     // we need #14072 to make sense of the generics.
1124     render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
1125     document_type_layout(w, cx, def_id);
1126 }
1127
1128 fn item_union(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, s: &clean::Union) {
1129     wrap_into_item_decl(w, |w| {
1130         wrap_item(w, "union", |w| {
1131             render_attributes_in_pre(w, it, "");
1132             render_union(w, it, Some(&s.generics), &s.fields, "", cx);
1133         });
1134     });
1135
1136     document(w, cx, it, None, HeadingOffset::H2);
1137
1138     let mut fields = s
1139         .fields
1140         .iter()
1141         .filter_map(|f| match *f.kind {
1142             clean::StructFieldItem(ref ty) => Some((f, ty)),
1143             _ => None,
1144         })
1145         .peekable();
1146     if fields.peek().is_some() {
1147         write!(
1148             w,
1149             "<h2 id=\"fields\" class=\"fields small-section-header\">\
1150                 Fields<a href=\"#fields\" class=\"anchor\">§</a>\
1151             </h2>"
1152         );
1153         for (field, ty) in fields {
1154             let name = field.name.expect("union field name");
1155             let id = format!("{}.{}", ItemType::StructField, name);
1156             write!(
1157                 w,
1158                 "<span id=\"{id}\" class=\"{shortty} small-section-header\">\
1159                      <a href=\"#{id}\" class=\"anchor field\">§</a>\
1160                      <code>{name}: {ty}</code>\
1161                  </span>",
1162                 id = id,
1163                 name = name,
1164                 shortty = ItemType::StructField,
1165                 ty = ty.print(cx),
1166             );
1167             if let Some(stability_class) = field.stability_class(cx.tcx()) {
1168                 write!(w, "<span class=\"stab {stab}\"></span>", stab = stability_class);
1169             }
1170             document(w, cx, field, Some(it), HeadingOffset::H3);
1171         }
1172     }
1173     let def_id = it.item_id.expect_def_id();
1174     render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
1175     document_type_layout(w, cx, def_id);
1176 }
1177
1178 fn print_tuple_struct_fields(w: &mut Buffer, cx: &Context<'_>, s: &[clean::Item]) {
1179     for (i, ty) in s.iter().enumerate() {
1180         if i > 0 {
1181             w.write_str(",&nbsp;");
1182         }
1183         match *ty.kind {
1184             clean::StrippedItem(box clean::StructFieldItem(_)) => w.write_str("_"),
1185             clean::StructFieldItem(ref ty) => write!(w, "{}", ty.print(cx)),
1186             _ => unreachable!(),
1187         }
1188     }
1189 }
1190
1191 fn item_enum(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, e: &clean::Enum) {
1192     let tcx = cx.tcx();
1193     let count_variants = e.variants().count();
1194     wrap_into_item_decl(w, |w| {
1195         wrap_item(w, "enum", |w| {
1196             render_attributes_in_pre(w, it, "");
1197             write!(
1198                 w,
1199                 "{}enum {}{}",
1200                 visibility_print_with_space(it.visibility(tcx), it.item_id, cx),
1201                 it.name.unwrap(),
1202                 e.generics.print(cx),
1203             );
1204             if !print_where_clause_and_check(w, &e.generics, cx) {
1205                 // If there wasn't a `where` clause, we add a whitespace.
1206                 w.write_str(" ");
1207             }
1208
1209             let variants_stripped = e.has_stripped_entries();
1210             if count_variants == 0 && !variants_stripped {
1211                 w.write_str("{}");
1212             } else {
1213                 w.write_str("{\n");
1214                 let toggle = should_hide_fields(count_variants);
1215                 if toggle {
1216                     toggle_open(w, format_args!("{} variants", count_variants));
1217                 }
1218                 for v in e.variants() {
1219                     w.write_str("    ");
1220                     let name = v.name.unwrap();
1221                     match *v.kind {
1222                         clean::VariantItem(ref var) => match var {
1223                             // FIXME(#101337): Show discriminant
1224                             clean::Variant::CLike(..) => write!(w, "{}", name),
1225                             clean::Variant::Tuple(ref s) => {
1226                                 write!(w, "{}(", name);
1227                                 print_tuple_struct_fields(w, cx, s);
1228                                 w.write_str(")");
1229                             }
1230                             clean::Variant::Struct(ref s) => {
1231                                 render_struct(
1232                                     w,
1233                                     v,
1234                                     None,
1235                                     s.ctor_kind,
1236                                     &s.fields,
1237                                     "    ",
1238                                     false,
1239                                     cx,
1240                                 );
1241                             }
1242                         },
1243                         _ => unreachable!(),
1244                     }
1245                     w.write_str(",\n");
1246                 }
1247
1248                 if variants_stripped {
1249                     w.write_str("    // some variants omitted\n");
1250                 }
1251                 if toggle {
1252                     toggle_close(w);
1253                 }
1254                 w.write_str("}");
1255             }
1256         });
1257     });
1258
1259     document(w, cx, it, None, HeadingOffset::H2);
1260
1261     if count_variants != 0 {
1262         write!(
1263             w,
1264             "<h2 id=\"variants\" class=\"variants small-section-header\">\
1265                 Variants{}<a href=\"#variants\" class=\"anchor\">§</a>\
1266             </h2>",
1267             document_non_exhaustive_header(it)
1268         );
1269         document_non_exhaustive(w, it);
1270         write!(w, "<div class=\"variants\">");
1271         for variant in e.variants() {
1272             let id = cx.derive_id(format!("{}.{}", ItemType::Variant, variant.name.unwrap()));
1273             write!(
1274                 w,
1275                 "<section id=\"{id}\" class=\"variant\">\
1276                     <a href=\"#{id}\" class=\"anchor\">§</a>",
1277                 id = id,
1278             );
1279             render_stability_since_raw_with_extra(
1280                 w,
1281                 variant.stable_since(tcx),
1282                 variant.const_stability(tcx),
1283                 it.stable_since(tcx),
1284                 it.const_stable_since(tcx),
1285                 " rightside",
1286             );
1287             write!(w, "<h3 class=\"code-header\">{name}", name = variant.name.unwrap());
1288             if let clean::VariantItem(clean::Variant::Tuple(ref s)) = *variant.kind {
1289                 w.write_str("(");
1290                 print_tuple_struct_fields(w, cx, s);
1291                 w.write_str(")");
1292             }
1293             w.write_str("</h3></section>");
1294
1295             use crate::clean::Variant;
1296
1297             let heading_and_fields = match &*variant.kind {
1298                 clean::VariantItem(Variant::Struct(s)) => Some(("Fields", &s.fields)),
1299                 // Documentation on tuple variant fields is rare, so to reduce noise we only emit
1300                 // the section if at least one field is documented.
1301                 clean::VariantItem(Variant::Tuple(fields))
1302                     if fields.iter().any(|f| f.doc_value().is_some()) =>
1303                 {
1304                     Some(("Tuple Fields", fields))
1305                 }
1306                 _ => None,
1307             };
1308
1309             if let Some((heading, fields)) = heading_and_fields {
1310                 let variant_id =
1311                     cx.derive_id(format!("{}.{}.fields", ItemType::Variant, variant.name.unwrap()));
1312                 write!(w, "<div class=\"sub-variant\" id=\"{id}\">", id = variant_id);
1313                 write!(w, "<h4>{heading}</h4>", heading = heading);
1314                 document_non_exhaustive(w, variant);
1315                 for field in fields {
1316                     match *field.kind {
1317                         clean::StrippedItem(box clean::StructFieldItem(_)) => {}
1318                         clean::StructFieldItem(ref ty) => {
1319                             let id = cx.derive_id(format!(
1320                                 "variant.{}.field.{}",
1321                                 variant.name.unwrap(),
1322                                 field.name.unwrap()
1323                             ));
1324                             write!(
1325                                 w,
1326                                 "<div class=\"sub-variant-field\">\
1327                                  <span id=\"{id}\" class=\"small-section-header\">\
1328                                      <a href=\"#{id}\" class=\"anchor field\">§</a>\
1329                                      <code>{f}:&nbsp;{t}</code>\
1330                                  </span>",
1331                                 id = id,
1332                                 f = field.name.unwrap(),
1333                                 t = ty.print(cx)
1334                             );
1335                             document(w, cx, field, Some(variant), HeadingOffset::H5);
1336                             write!(w, "</div>");
1337                         }
1338                         _ => unreachable!(),
1339                     }
1340                 }
1341                 w.write_str("</div>");
1342             }
1343
1344             document(w, cx, variant, Some(it), HeadingOffset::H4);
1345         }
1346         write!(w, "</div>");
1347     }
1348     let def_id = it.item_id.expect_def_id();
1349     render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
1350     document_type_layout(w, cx, def_id);
1351 }
1352
1353 fn item_macro(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, t: &clean::Macro) {
1354     wrap_into_item_decl(w, |w| {
1355         highlight::render_macro_with_highlighting(&t.source, w);
1356     });
1357     document(w, cx, it, None, HeadingOffset::H2)
1358 }
1359
1360 fn item_proc_macro(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, m: &clean::ProcMacro) {
1361     wrap_into_item_decl(w, |w| {
1362         let name = it.name.expect("proc-macros always have names");
1363         match m.kind {
1364             MacroKind::Bang => {
1365                 wrap_item(w, "macro", |w| {
1366                     write!(w, "{}!() {{ /* proc-macro */ }}", name);
1367                 });
1368             }
1369             MacroKind::Attr => {
1370                 wrap_item(w, "attr", |w| {
1371                     write!(w, "#[{}]", name);
1372                 });
1373             }
1374             MacroKind::Derive => {
1375                 wrap_item(w, "derive", |w| {
1376                     write!(w, "#[derive({})]", name);
1377                     if !m.helpers.is_empty() {
1378                         w.push_str("\n{\n");
1379                         w.push_str("    // Attributes available to this derive:\n");
1380                         for attr in &m.helpers {
1381                             writeln!(w, "    #[{}]", attr);
1382                         }
1383                         w.push_str("}\n");
1384                     }
1385                 });
1386             }
1387         }
1388     });
1389     document(w, cx, it, None, HeadingOffset::H2)
1390 }
1391
1392 fn item_primitive(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item) {
1393     let def_id = it.item_id.expect_def_id();
1394     document(w, cx, it, None, HeadingOffset::H2);
1395     if it.name.map(|n| n.as_str() != "reference").unwrap_or(false) {
1396         render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
1397     } else {
1398         // We handle the "reference" primitive type on its own because we only want to list
1399         // implementations on generic types.
1400         let shared = Rc::clone(&cx.shared);
1401         let (concrete, synthetic, blanket_impl) = get_filtered_impls_for_reference(&shared, it);
1402
1403         render_all_impls(w, cx, it, &concrete, &synthetic, &blanket_impl);
1404     }
1405 }
1406
1407 fn item_constant(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, c: &clean::Constant) {
1408     wrap_into_item_decl(w, |w| {
1409         wrap_item(w, "const", |w| {
1410             let tcx = cx.tcx();
1411             render_attributes_in_code(w, it);
1412
1413             write!(
1414                 w,
1415                 "{vis}const {name}: {typ}",
1416                 vis = visibility_print_with_space(it.visibility(tcx), it.item_id, cx),
1417                 name = it.name.unwrap(),
1418                 typ = c.type_.print(cx),
1419             );
1420
1421             // FIXME: The code below now prints
1422             //            ` = _; // 100i32`
1423             //        if the expression is
1424             //            `50 + 50`
1425             //        which looks just wrong.
1426             //        Should we print
1427             //            ` = 100i32;`
1428             //        instead?
1429
1430             let value = c.value(tcx);
1431             let is_literal = c.is_literal(tcx);
1432             let expr = c.expr(tcx);
1433             if value.is_some() || is_literal {
1434                 write!(w, " = {expr};", expr = Escape(&expr));
1435             } else {
1436                 w.write_str(";");
1437             }
1438
1439             if !is_literal {
1440                 if let Some(value) = &value {
1441                     let value_lowercase = value.to_lowercase();
1442                     let expr_lowercase = expr.to_lowercase();
1443
1444                     if value_lowercase != expr_lowercase
1445                         && value_lowercase.trim_end_matches("i32") != expr_lowercase
1446                     {
1447                         write!(w, " // {value}", value = Escape(value));
1448                     }
1449                 }
1450             }
1451         });
1452     });
1453
1454     document(w, cx, it, None, HeadingOffset::H2)
1455 }
1456
1457 fn item_struct(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, s: &clean::Struct) {
1458     wrap_into_item_decl(w, |w| {
1459         wrap_item(w, "struct", |w| {
1460             render_attributes_in_code(w, it);
1461             render_struct(w, it, Some(&s.generics), s.ctor_kind, &s.fields, "", true, cx);
1462         });
1463     });
1464
1465     document(w, cx, it, None, HeadingOffset::H2);
1466
1467     let mut fields = s
1468         .fields
1469         .iter()
1470         .filter_map(|f| match *f.kind {
1471             clean::StructFieldItem(ref ty) => Some((f, ty)),
1472             _ => None,
1473         })
1474         .peekable();
1475     if let None | Some(CtorKind::Fn) = s.ctor_kind {
1476         if fields.peek().is_some() {
1477             write!(
1478                 w,
1479                 "<h2 id=\"fields\" class=\"fields small-section-header\">\
1480                      {}{}<a href=\"#fields\" class=\"anchor\">§</a>\
1481                  </h2>",
1482                 if s.ctor_kind.is_none() { "Fields" } else { "Tuple Fields" },
1483                 document_non_exhaustive_header(it)
1484             );
1485             document_non_exhaustive(w, it);
1486             for (index, (field, ty)) in fields.enumerate() {
1487                 let field_name =
1488                     field.name.map_or_else(|| index.to_string(), |sym| sym.as_str().to_string());
1489                 let id = cx.derive_id(format!("{}.{}", ItemType::StructField, field_name));
1490                 write!(
1491                     w,
1492                     "<span id=\"{id}\" class=\"{item_type} small-section-header\">\
1493                          <a href=\"#{id}\" class=\"anchor field\">§</a>\
1494                          <code>{name}: {ty}</code>\
1495                      </span>",
1496                     item_type = ItemType::StructField,
1497                     id = id,
1498                     name = field_name,
1499                     ty = ty.print(cx)
1500                 );
1501                 document(w, cx, field, Some(it), HeadingOffset::H3);
1502             }
1503         }
1504     }
1505     let def_id = it.item_id.expect_def_id();
1506     render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
1507     document_type_layout(w, cx, def_id);
1508 }
1509
1510 fn item_static(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, s: &clean::Static) {
1511     wrap_into_item_decl(w, |w| {
1512         wrap_item(w, "static", |w| {
1513             render_attributes_in_code(w, it);
1514             write!(
1515                 w,
1516                 "{vis}static {mutability}{name}: {typ}",
1517                 vis = visibility_print_with_space(it.visibility(cx.tcx()), it.item_id, cx),
1518                 mutability = s.mutability.print_with_space(),
1519                 name = it.name.unwrap(),
1520                 typ = s.type_.print(cx)
1521             );
1522         });
1523     });
1524     document(w, cx, it, None, HeadingOffset::H2)
1525 }
1526
1527 fn item_foreign_type(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item) {
1528     wrap_into_item_decl(w, |w| {
1529         wrap_item(w, "foreigntype", |w| {
1530             w.write_str("extern {\n");
1531             render_attributes_in_code(w, it);
1532             write!(
1533                 w,
1534                 "    {}type {};\n}}",
1535                 visibility_print_with_space(it.visibility(cx.tcx()), it.item_id, cx),
1536                 it.name.unwrap(),
1537             );
1538         });
1539     });
1540
1541     document(w, cx, it, None, HeadingOffset::H2);
1542
1543     render_assoc_items(w, cx, it, it.item_id.expect_def_id(), AssocItemRender::All)
1544 }
1545
1546 fn item_keyword(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item) {
1547     document(w, cx, it, None, HeadingOffset::H2)
1548 }
1549
1550 /// Compare two strings treating multi-digit numbers as single units (i.e. natural sort order).
1551 pub(crate) fn compare_names(mut lhs: &str, mut rhs: &str) -> Ordering {
1552     /// Takes a non-numeric and a numeric part from the given &str.
1553     fn take_parts<'a>(s: &mut &'a str) -> (&'a str, &'a str) {
1554         let i = s.find(|c: char| c.is_ascii_digit());
1555         let (a, b) = s.split_at(i.unwrap_or(s.len()));
1556         let i = b.find(|c: char| !c.is_ascii_digit());
1557         let (b, c) = b.split_at(i.unwrap_or(b.len()));
1558         *s = c;
1559         (a, b)
1560     }
1561
1562     while !lhs.is_empty() || !rhs.is_empty() {
1563         let (la, lb) = take_parts(&mut lhs);
1564         let (ra, rb) = take_parts(&mut rhs);
1565         // First process the non-numeric part.
1566         match la.cmp(ra) {
1567             Ordering::Equal => (),
1568             x => return x,
1569         }
1570         // Then process the numeric part, if both sides have one (and they fit in a u64).
1571         if let (Ok(ln), Ok(rn)) = (lb.parse::<u64>(), rb.parse::<u64>()) {
1572             match ln.cmp(&rn) {
1573                 Ordering::Equal => (),
1574                 x => return x,
1575             }
1576         }
1577         // Then process the numeric part again, but this time as strings.
1578         match lb.cmp(rb) {
1579             Ordering::Equal => (),
1580             x => return x,
1581         }
1582     }
1583
1584     Ordering::Equal
1585 }
1586
1587 pub(super) fn full_path(cx: &Context<'_>, item: &clean::Item) -> String {
1588     let mut s = join_with_double_colon(&cx.current);
1589     s.push_str("::");
1590     s.push_str(item.name.unwrap().as_str());
1591     s
1592 }
1593
1594 pub(super) fn item_path(ty: ItemType, name: &str) -> String {
1595     match ty {
1596         ItemType::Module => format!("{}index.html", ensure_trailing_slash(name)),
1597         _ => format!("{}.{}.html", ty, name),
1598     }
1599 }
1600
1601 fn bounds(t_bounds: &[clean::GenericBound], trait_alias: bool, cx: &Context<'_>) -> String {
1602     let mut bounds = String::new();
1603     if !t_bounds.is_empty() {
1604         if !trait_alias {
1605             bounds.push_str(": ");
1606         }
1607         for (i, p) in t_bounds.iter().enumerate() {
1608             if i > 0 {
1609                 bounds.push_str(" + ");
1610             }
1611             bounds.push_str(&p.print(cx).to_string());
1612         }
1613     }
1614     bounds
1615 }
1616
1617 fn wrap_into_item_decl<F>(w: &mut Buffer, f: F)
1618 where
1619     F: FnOnce(&mut Buffer),
1620 {
1621     w.write_str("<div class=\"item-decl\">");
1622     f(w);
1623     w.write_str("</div>")
1624 }
1625
1626 fn wrap_item<F>(w: &mut Buffer, item_name: &str, f: F)
1627 where
1628     F: FnOnce(&mut Buffer),
1629 {
1630     w.write_fmt(format_args!("<pre class=\"rust {}\"><code>", item_name));
1631     f(w);
1632     w.write_str("</code></pre>");
1633 }
1634
1635 fn compare_impl<'a, 'b>(lhs: &'a &&Impl, rhs: &'b &&Impl, cx: &Context<'_>) -> Ordering {
1636     let lhss = format!("{}", lhs.inner_impl().print(false, cx));
1637     let rhss = format!("{}", rhs.inner_impl().print(false, cx));
1638
1639     // lhs and rhs are formatted as HTML, which may be unnecessary
1640     compare_names(&lhss, &rhss)
1641 }
1642
1643 fn render_implementor(
1644     cx: &mut Context<'_>,
1645     implementor: &Impl,
1646     trait_: &clean::Item,
1647     w: &mut Buffer,
1648     implementor_dups: &FxHashMap<Symbol, (DefId, bool)>,
1649     aliases: &[String],
1650 ) {
1651     // If there's already another implementor that has the same abridged name, use the
1652     // full path, for example in `std::iter::ExactSizeIterator`
1653     let use_absolute = match implementor.inner_impl().for_ {
1654         clean::Type::Path { ref path, .. }
1655         | clean::BorrowedRef { type_: box clean::Type::Path { ref path, .. }, .. }
1656             if !path.is_assoc_ty() =>
1657         {
1658             implementor_dups[&path.last()].1
1659         }
1660         _ => false,
1661     };
1662     render_impl(
1663         w,
1664         cx,
1665         implementor,
1666         trait_,
1667         AssocItemLink::Anchor(None),
1668         RenderMode::Normal,
1669         Some(use_absolute),
1670         aliases,
1671         ImplRenderingParameters {
1672             show_def_docs: false,
1673             show_default_items: false,
1674             show_non_assoc_items: false,
1675             toggle_open_by_default: false,
1676         },
1677     );
1678 }
1679
1680 fn render_union(
1681     w: &mut Buffer,
1682     it: &clean::Item,
1683     g: Option<&clean::Generics>,
1684     fields: &[clean::Item],
1685     tab: &str,
1686     cx: &Context<'_>,
1687 ) {
1688     let tcx = cx.tcx();
1689     write!(
1690         w,
1691         "{}union {}",
1692         visibility_print_with_space(it.visibility(tcx), it.item_id, cx),
1693         it.name.unwrap(),
1694     );
1695
1696     let where_displayed = g
1697         .map(|g| {
1698             write!(w, "{}", g.print(cx));
1699             print_where_clause_and_check(w, g, cx)
1700         })
1701         .unwrap_or(false);
1702
1703     // If there wasn't a `where` clause, we add a whitespace.
1704     if !where_displayed {
1705         w.write_str(" ");
1706     }
1707
1708     write!(w, "{{\n{}", tab);
1709     let count_fields =
1710         fields.iter().filter(|f| matches!(*f.kind, clean::StructFieldItem(..))).count();
1711     let toggle = should_hide_fields(count_fields);
1712     if toggle {
1713         toggle_open(w, format_args!("{} fields", count_fields));
1714     }
1715
1716     for field in fields {
1717         if let clean::StructFieldItem(ref ty) = *field.kind {
1718             write!(
1719                 w,
1720                 "    {}{}: {},\n{}",
1721                 visibility_print_with_space(field.visibility(tcx), field.item_id, cx),
1722                 field.name.unwrap(),
1723                 ty.print(cx),
1724                 tab
1725             );
1726         }
1727     }
1728
1729     if it.has_stripped_entries().unwrap() {
1730         write!(w, "    /* private fields */\n{}", tab);
1731     }
1732     if toggle {
1733         toggle_close(w);
1734     }
1735     w.write_str("}");
1736 }
1737
1738 fn render_struct(
1739     w: &mut Buffer,
1740     it: &clean::Item,
1741     g: Option<&clean::Generics>,
1742     ty: Option<CtorKind>,
1743     fields: &[clean::Item],
1744     tab: &str,
1745     structhead: bool,
1746     cx: &Context<'_>,
1747 ) {
1748     let tcx = cx.tcx();
1749     write!(
1750         w,
1751         "{}{}{}",
1752         visibility_print_with_space(it.visibility(tcx), it.item_id, cx),
1753         if structhead { "struct " } else { "" },
1754         it.name.unwrap()
1755     );
1756     if let Some(g) = g {
1757         write!(w, "{}", g.print(cx))
1758     }
1759     match ty {
1760         None => {
1761             let where_diplayed = g.map(|g| print_where_clause_and_check(w, g, cx)).unwrap_or(false);
1762
1763             // If there wasn't a `where` clause, we add a whitespace.
1764             if !where_diplayed {
1765                 w.write_str(" {");
1766             } else {
1767                 w.write_str("{");
1768             }
1769             let count_fields =
1770                 fields.iter().filter(|f| matches!(*f.kind, clean::StructFieldItem(..))).count();
1771             let has_visible_fields = count_fields > 0;
1772             let toggle = should_hide_fields(count_fields);
1773             if toggle {
1774                 toggle_open(w, format_args!("{} fields", count_fields));
1775             }
1776             for field in fields {
1777                 if let clean::StructFieldItem(ref ty) = *field.kind {
1778                     write!(
1779                         w,
1780                         "\n{}    {}{}: {},",
1781                         tab,
1782                         visibility_print_with_space(field.visibility(tcx), field.item_id, cx),
1783                         field.name.unwrap(),
1784                         ty.print(cx),
1785                     );
1786                 }
1787             }
1788
1789             if has_visible_fields {
1790                 if it.has_stripped_entries().unwrap() {
1791                     write!(w, "\n{}    /* private fields */", tab);
1792                 }
1793                 write!(w, "\n{}", tab);
1794             } else if it.has_stripped_entries().unwrap() {
1795                 write!(w, " /* private fields */ ");
1796             }
1797             if toggle {
1798                 toggle_close(w);
1799             }
1800             w.write_str("}");
1801         }
1802         Some(CtorKind::Fn) => {
1803             w.write_str("(");
1804             for (i, field) in fields.iter().enumerate() {
1805                 if i > 0 {
1806                     w.write_str(", ");
1807                 }
1808                 match *field.kind {
1809                     clean::StrippedItem(box clean::StructFieldItem(..)) => write!(w, "_"),
1810                     clean::StructFieldItem(ref ty) => {
1811                         write!(
1812                             w,
1813                             "{}{}",
1814                             visibility_print_with_space(field.visibility(tcx), field.item_id, cx),
1815                             ty.print(cx),
1816                         )
1817                     }
1818                     _ => unreachable!(),
1819                 }
1820             }
1821             w.write_str(")");
1822             if let Some(g) = g {
1823                 write!(w, "{}", print_where_clause(g, cx, 0, Ending::NoNewline));
1824             }
1825             // We only want a ";" when we are displaying a tuple struct, not a variant tuple struct.
1826             if structhead {
1827                 w.write_str(";");
1828             }
1829         }
1830         Some(CtorKind::Const) => {
1831             // Needed for PhantomData.
1832             if let Some(g) = g {
1833                 write!(w, "{}", print_where_clause(g, cx, 0, Ending::NoNewline));
1834             }
1835             w.write_str(";");
1836         }
1837     }
1838 }
1839
1840 fn document_non_exhaustive_header(item: &clean::Item) -> &str {
1841     if item.is_non_exhaustive() { " (Non-exhaustive)" } else { "" }
1842 }
1843
1844 fn document_non_exhaustive(w: &mut Buffer, item: &clean::Item) {
1845     if item.is_non_exhaustive() {
1846         write!(
1847             w,
1848             "<details class=\"rustdoc-toggle non-exhaustive\">\
1849                  <summary class=\"hideme\"><span>{}</span></summary>\
1850                  <div class=\"docblock\">",
1851             {
1852                 if item.is_struct() {
1853                     "This struct is marked as non-exhaustive"
1854                 } else if item.is_enum() {
1855                     "This enum is marked as non-exhaustive"
1856                 } else if item.is_variant() {
1857                     "This variant is marked as non-exhaustive"
1858                 } else {
1859                     "This type is marked as non-exhaustive"
1860                 }
1861             }
1862         );
1863
1864         if item.is_struct() {
1865             w.write_str(
1866                 "Non-exhaustive structs could have additional fields added in future. \
1867                  Therefore, non-exhaustive structs cannot be constructed in external crates \
1868                  using the traditional <code>Struct { .. }</code> syntax; cannot be \
1869                  matched against without a wildcard <code>..</code>; and \
1870                  struct update syntax will not work.",
1871             );
1872         } else if item.is_enum() {
1873             w.write_str(
1874                 "Non-exhaustive enums could have additional variants added in future. \
1875                  Therefore, when matching against variants of non-exhaustive enums, an \
1876                  extra wildcard arm must be added to account for any future variants.",
1877             );
1878         } else if item.is_variant() {
1879             w.write_str(
1880                 "Non-exhaustive enum variants could have additional fields added in future. \
1881                  Therefore, non-exhaustive enum variants cannot be constructed in external \
1882                  crates and cannot be matched against.",
1883             );
1884         } else {
1885             w.write_str(
1886                 "This type will require a wildcard arm in any match statements or constructors.",
1887             );
1888         }
1889
1890         w.write_str("</div></details>");
1891     }
1892 }
1893
1894 fn document_type_layout(w: &mut Buffer, cx: &Context<'_>, ty_def_id: DefId) {
1895     fn write_size_of_layout(w: &mut Buffer, layout: &LayoutS<VariantIdx>, tag_size: u64) {
1896         if layout.abi.is_unsized() {
1897             write!(w, "(unsized)");
1898         } else {
1899             let bytes = layout.size.bytes() - tag_size;
1900             write!(w, "{size} byte{pl}", size = bytes, pl = if bytes == 1 { "" } else { "s" },);
1901         }
1902     }
1903
1904     if !cx.shared.show_type_layout {
1905         return;
1906     }
1907
1908     writeln!(
1909         w,
1910         "<h2 id=\"layout\" class=\"small-section-header\"> \
1911         Layout<a href=\"#layout\" class=\"anchor\">§</a></h2>"
1912     );
1913     writeln!(w, "<div class=\"docblock\">");
1914
1915     let tcx = cx.tcx();
1916     let param_env = tcx.param_env(ty_def_id);
1917     let ty = tcx.type_of(ty_def_id);
1918     match tcx.layout_of(param_env.and(ty)) {
1919         Ok(ty_layout) => {
1920             writeln!(
1921                 w,
1922                 "<div class=\"warning\"><p><strong>Note:</strong> Most layout information is \
1923                  <strong>completely unstable</strong> and may even differ between compilations. \
1924                  The only exception is types with certain <code>repr(...)</code> attributes. \
1925                  Please see the Rust Reference’s \
1926                  <a href=\"https://doc.rust-lang.org/reference/type-layout.html\">“Type Layout”</a> \
1927                  chapter for details on type layout guarantees.</p></div>"
1928             );
1929             w.write_str("<p><strong>Size:</strong> ");
1930             write_size_of_layout(w, &ty_layout.layout.0, 0);
1931             writeln!(w, "</p>");
1932             if let Variants::Multiple { variants, tag, tag_encoding, .. } =
1933                 &ty_layout.layout.variants()
1934             {
1935                 if !variants.is_empty() {
1936                     w.write_str(
1937                         "<p><strong>Size for each variant:</strong></p>\
1938                             <ul>",
1939                     );
1940
1941                     let Adt(adt, _) = ty_layout.ty.kind() else {
1942                         span_bug!(tcx.def_span(ty_def_id), "not an adt")
1943                     };
1944
1945                     let tag_size = if let TagEncoding::Niche { .. } = tag_encoding {
1946                         0
1947                     } else if let Primitive::Int(i, _) = tag.primitive() {
1948                         i.size().bytes()
1949                     } else {
1950                         span_bug!(tcx.def_span(ty_def_id), "tag is neither niche nor int")
1951                     };
1952
1953                     for (index, layout) in variants.iter_enumerated() {
1954                         let name = adt.variant(index).name;
1955                         write!(w, "<li><code>{name}</code>: ", name = name);
1956                         write_size_of_layout(w, layout, tag_size);
1957                         writeln!(w, "</li>");
1958                     }
1959                     w.write_str("</ul>");
1960                 }
1961             }
1962         }
1963         // This kind of layout error can occur with valid code, e.g. if you try to
1964         // get the layout of a generic type such as `Vec<T>`.
1965         Err(LayoutError::Unknown(_)) => {
1966             writeln!(
1967                 w,
1968                 "<p><strong>Note:</strong> Unable to compute type layout, \
1969                  possibly due to this type having generic parameters. \
1970                  Layout can only be computed for concrete, fully-instantiated types.</p>"
1971             );
1972         }
1973         // This kind of error probably can't happen with valid code, but we don't
1974         // want to panic and prevent the docs from building, so we just let the
1975         // user know that we couldn't compute the layout.
1976         Err(LayoutError::SizeOverflow(_)) => {
1977             writeln!(
1978                 w,
1979                 "<p><strong>Note:</strong> Encountered an error during type layout; \
1980                  the type was too big.</p>"
1981             );
1982         }
1983         Err(LayoutError::NormalizationFailure(_, _)) => {
1984             writeln!(
1985                 w,
1986                 "<p><strong>Note:</strong> Encountered an error during type layout; \
1987                 the type failed to be normalized.</p>"
1988             )
1989         }
1990     }
1991
1992     writeln!(w, "</div>");
1993 }
1994
1995 fn pluralize(count: usize) -> &'static str {
1996     if count > 1 { "s" } else { "" }
1997 }