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