Emit valid HTML from rustdoc

Previously, tidy-html5 (`tidy`) would complain about a few things in our
HTML. The main thing is that `<summary>` tags can't contain `<div>`s.
That's easily fixed by changing out the `<div>`s for `<span>`s with
`display: block`.

However, there's also a rule that `<span>`s can't contain heading
elements. `<span>` permits only "phrasing content"
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/span, and
`<h3>` (and friends) are "Flow content, heading content, palpable
content".
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/Heading_Elements

We have a wrapping `<div>` that goes around each `<h3>`/`<h4>`,
etc. We turn that into a `<section>` rather than a `<span>` because
`<section>` permits "flow content".
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/section

After this change we get only three warnings from tidy, run on
struct.String.html:

line 6 column 10790 - Warning: trimming empty <span>
line 1 column 1118 - Warning: <link> proprietary attribute "disabled"
line 1 column 1193 - Warning: <link> proprietary attribute "disabled"

The empty `<span>` is a known issue - there's a span in front of the
search box to work around a strange Safari issue.

The `<link>` attributes are the non-default stylesheets. We can probably
refactor theme application to avoid using this proprietary "disabled"
attribute.

src/librustdoc/html/render/mod.rs

@@ -1265,7 +1265,7 @@ fn notable_traits_decl(decl: &clean::FnDecl, cx: &Context<'_>) -> String {
                         if out.is_empty() {
                             write!(
                                 &mut out,
-                                "<div class=\"notable\">Notable traits for {}</div>\
+                                "<span class=\"notable\">Notable traits for {}</span>\
                              <code class=\"content\">",
                                 impl_.for_.print(cx)
                             );
@@ -1297,9 +1297,9 @@ fn notable_traits_decl(decl: &clean::FnDecl, cx: &Context<'_>) -> String {
         out.insert_str(
             0,
             "<span class=\"notable-traits\"><span class=\"notable-traits-tooltip\">ⓘ\
-            <div class=\"notable-traits-tooltiptext\"><span class=\"docblock\">",
+            <span class=\"notable-traits-tooltiptext\"><span class=\"docblock\">",
         );
-        out.push_str("</code></span></div></span></span>");
+        out.push_str("</code></span></span></span></span>");
     }
 
     out.into_inner()
@@ -1431,7 +1431,7 @@ fn render_impl(
                         .map(|item| format!("{}.{}", item.type_(), name));
                     write!(
                         w,
-                        "<div id=\"{}\" class=\"{}{} has-srclink\">",
+                        "<section id=\"{}\" class=\"{}{} has-srclink\">",
                         id, item_type, in_trait_class,
                     );
                     render_rightside(w, cx, item, containing_item, render_mode);
@@ -1446,15 +1446,15 @@ fn render_impl(
                         render_mode,
                     );
                     w.write_str("</h4>");
-                    w.write_str("</div>");
+                    w.write_str("</section>");
                 }
             }
             clean::TypedefItem(ref tydef, _) => {
                 let source_id = format!("{}.{}", ItemType::AssocType, name);
                 let id = cx.derive_id(source_id.clone());
                 write!(
                     w,
-                    "<div id=\"{}\" class=\"{}{} has-srclink\">",
+                    "<section id=\"{}\" class=\"{}{} has-srclink\">",
                     id, item_type, in_trait_class
                 );
                 write!(w, "<a href=\"#{}\" class=\"anchor\"></a>", id);
@@ -1469,14 +1469,14 @@ fn render_impl(
                     cx,
                 );
                 w.write_str("</h4>");
-                w.write_str("</div>");
+                w.write_str("</section>");
             }
             clean::AssocConstItem(ref ty, _) => {
                 let source_id = format!("{}.{}", item_type, name);
                 let id = cx.derive_id(source_id.clone());
                 write!(
                     w,
-                    "<div id=\"{}\" class=\"{}{} has-srclink\">",
+                    "<section id=\"{}\" class=\"{}{} has-srclink\">",
                     id, item_type, in_trait_class
                 );
                 render_rightside(w, cx, item, containing_item, render_mode);
@@ -1491,12 +1491,12 @@ fn render_impl(
                     cx,
                 );
                 w.write_str("</h4>");
-                w.write_str("</div>");
+                w.write_str("</section>");
             }
             clean::AssocTypeItem(ref bounds, ref default) => {
                 let source_id = format!("{}.{}", item_type, name);
                 let id = cx.derive_id(source_id.clone());
-                write!(w, "<div id=\"{}\" class=\"{}{}\">", id, item_type, in_trait_class,);
+                write!(w, "<section id=\"{}\" class=\"{}{}\">", id, item_type, in_trait_class,);
                 write!(w, "<a href=\"#{}\" class=\"anchor\"></a>", id);
                 w.write_str("<h4 class=\"code-header\">");
                 assoc_type(
@@ -1509,7 +1509,7 @@ fn render_impl(
                     cx,
                 );
                 w.write_str("</h4>");
-                w.write_str("</div>");
+                w.write_str("</section>");
             }
             clean::StrippedItem(..) => return,
             _ => panic!("can't make docs for trait item with name {:?}", item.name),
@@ -1668,21 +1668,23 @@ fn render_rightside(
         RenderMode::ForDeref { .. } => (None, None),
     };
 
-    write!(w, "<div class=\"rightside\">");
+    let mut rightside = Buffer::new();
     let has_stability = render_stability_since_raw(
-        w,
+        &mut rightside,
         item.stable_since(tcx),
         const_stability,
         containing_item.stable_since(tcx),
         const_stable_since,
     );
-    let mut tmp_buf = Buffer::empty_from(w);
-    write_srclink(cx, item, &mut tmp_buf);
-    if has_stability && !tmp_buf.is_empty() {
-        w.write_str(" · ");
+    let mut srclink = Buffer::empty_from(w);
+    write_srclink(cx, item, &mut srclink);
+    if has_stability && !srclink.is_empty() {
+        rightside.write_str(" · ");
+    }
+    rightside.push_buffer(srclink);
+    if !rightside.is_empty() {
+        write!(w, "<span class=\"rightside\">{}</span>", rightside.into_inner());
     }
-    w.push_buffer(tmp_buf);
-    w.write_str("</div>");
 }
 
 pub(crate) fn render_impl_summary(
@@ -1713,7 +1715,7 @@ pub(crate) fn render_impl_summary(
     } else {
         format!(" data-aliases=\"{}\"", aliases.join(","))
     };
-    write!(w, "<div id=\"{}\" class=\"impl has-srclink\"{}>", id, aliases);
+    write!(w, "<section id=\"{}\" class=\"impl has-srclink\"{}>", id, aliases);
     render_rightside(w, cx, &i.impl_item, containing_item, RenderMode::Normal);
     write!(w, "<a href=\"#{}\" class=\"anchor\"></a>", id);
     write!(w, "<h3 class=\"code-header in-band\">");
@@ -1737,11 +1739,11 @@ pub(crate) fn render_impl_summary(
     let is_trait = i.inner_impl().trait_.is_some();
     if is_trait {
         if let Some(portability) = portability(&i.impl_item, Some(parent)) {
-            write!(w, "<div class=\"item-info\">{}</div>", portability);
+            write!(w, "<span class=\"item-info\">{}</span>", portability);
         }
     }
 
-    w.write_str("</div>");
+    w.write_str("</section>");
 }
 
 fn print_sidebar(cx: &Context<'_>, it: &clean::Item, buffer: &mut Buffer) {
@@ -1802,19 +1804,9 @@ fn print_sidebar(cx: &Context<'_>, it: &clean::Item, buffer: &mut Buffer) {
     // to navigate the documentation (though slightly inefficiently).
 
     if !it.is_mod() {
-        buffer.write_str("<h2 class=\"location\">In ");
-        for (i, name) in cx.current.iter().take(parentlen).enumerate() {
-            if i > 0 {
-                buffer.write_str("::<wbr>");
-            }
-            write!(
-                buffer,
-                "<a href=\"{}index.html\">{}</a>",
-                &cx.root_path()[..(cx.current.len() - i - 1) * 3],
-                *name
-            );
-        }
-        buffer.write_str("</h2>");
+        let path: String = cx.current.iter().map(|s| s.as_str()).intersperse("::").collect();
+
+        write!(buffer, "<h2 class=\"location\"><a href=\"index.html\">In {}</a></h2>", path);
     }
 
     // Sidebar refers to the enclosing module, not this module.

src/librustdoc/html/static/css/rustdoc.css

@@ -1336,6 +1336,7 @@ h3.variant {
 	margin-bottom: 13px;
 	font-size: 1.1875rem;
 	font-weight: 600;
+	display: block;
 }
 
 .notable-traits .docblock code.content{

src/test/rustdoc/async-fn.rs

@@ -77,12 +77,12 @@ struct AsyncFdReadyGuard<'a, T> { x: &'a T }
 
 impl Foo {
     // @has async_fn/struct.Foo.html
-    // @has - '//div[@class="method has-srclink"]' 'pub async fn complicated_lifetimes( &self, context: &impl Bar) -> impl Iterator<Item = &usize>'
+    // @has - '//*[@class="method has-srclink"]' 'pub async fn complicated_lifetimes( &self, context: &impl Bar) -> impl Iterator<Item = &usize>'
     pub async fn complicated_lifetimes(&self, context: &impl Bar) -> impl Iterator<Item = &usize> {}
     // taken from `tokio` as an example of a method that was particularly bad before
-    // @has - '//div[@class="method has-srclink"]' "pub async fn readable<T>(&self) -> Result<AsyncFdReadyGuard<'_, T>, ()>"
+    // @has - '//*[@class="method has-srclink"]' "pub async fn readable<T>(&self) -> Result<AsyncFdReadyGuard<'_, T>, ()>"
     pub async fn readable<T>(&self) -> Result<AsyncFdReadyGuard<'_, T>, ()> {}
-    // @has - '//div[@class="method has-srclink"]' "pub async fn mut_self(&mut self)"
+    // @has - '//*[@class="method has-srclink"]' "pub async fn mut_self(&mut self)"
     pub async fn mut_self(&mut self) {}
 }
 

src/test/rustdoc/auto_aliases.rs

@@ -1,6 +1,6 @@
 #![feature(auto_traits)]
 
-// @has auto_aliases/trait.Bar.html '//div[@data-aliases="auto_aliases::Foo"]' 'impl Bar for Foo'
+// @has auto_aliases/trait.Bar.html '//*[@data-aliases="auto_aliases::Foo"]' 'impl Bar for Foo'
 pub struct Foo;
 
 pub auto trait Bar {}

src/test/rustdoc/blanket-reexport-item.rs

@@ -1,6 +1,6 @@
 #![crate_name = "foo"]
 
-// @has foo/struct.S.html '//div[@id="impl-Into%3CU%3E"]//h3[@class="code-header in-band"]' 'impl<T, U> Into<U> for T'
+// @has foo/struct.S.html '//*[@id="impl-Into%3CU%3E"]//h3[@class="code-header in-band"]' 'impl<T, U> Into<U> for T'
 pub struct S2 {}
 mod m {
     pub struct S {}

src/test/rustdoc/const-display.rs

@@ -49,19 +49,19 @@ pub const unsafe fn bar_not_gated() -> u32 { 42 }
 pub struct Foo;
 
 impl Foo {
-    // @has 'foo/struct.Foo.html' '//div[@id="method.gated"]/h4[@class="code-header"]' 'pub fn gated() -> u32'
+    // @has 'foo/struct.Foo.html' '//*[@id="method.gated"]/h4[@class="code-header"]' 'pub fn gated() -> u32'
     // @has - '//span[@class="since"]' '1.0.0 (const: unstable)'
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_unstable(feature="foo", issue = "none")]
     pub const fn gated() -> u32 { 42 }
 
-    // @has 'foo/struct.Foo.html' '//div[@id="method.gated_unsafe"]/h4[@class="code-header"]' 'pub unsafe fn gated_unsafe() -> u32'
+    // @has 'foo/struct.Foo.html' '//*[@id="method.gated_unsafe"]/h4[@class="code-header"]' 'pub unsafe fn gated_unsafe() -> u32'
     // @has - '//span[@class="since"]' '1.0.0 (const: unstable)'
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_unstable(feature="foo", issue = "none")]
     pub const unsafe fn gated_unsafe() -> u32 { 42 }
 
-    // @has 'foo/struct.Foo.html' '//div[@id="method.stable_impl"]/h4[@class="code-header"]' 'pub const fn stable_impl() -> u32'
+    // @has 'foo/struct.Foo.html' '//*[@id="method.stable_impl"]/h4[@class="code-header"]' 'pub const fn stable_impl() -> u32'
     // @has - '//span[@class="since"]' '1.0.0 (const: 1.2.0)'
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_stable(feature = "rust1", since = "1.2.0")]

src/test/rustdoc/const-generics/add-impl.rs

@@ -7,7 +7,7 @@ pub struct Simd<T, const WIDTH: usize> {
     inner: T,
 }
 
-// @has foo/struct.Simd.html '//div[@id="trait-implementations-list"]//div/h3[@class="code-header in-band"]' 'impl Add<Simd<u8, 16_usize>> for Simd<u8, 16>'
+// @has foo/struct.Simd.html '//div[@id="trait-implementations-list"]//h3[@class="code-header in-band"]' 'impl Add<Simd<u8, 16_usize>> for Simd<u8, 16>'
 impl Add for Simd<u8, 16> {
     type Output = Self;
 

src/test/rustdoc/const-generics/const-generic-slice.rs

@@ -5,7 +5,7 @@ pub trait Array {
 }
 
 // @has foo/trait.Array.html
-// @has - '//div[@class="impl has-srclink"]' 'impl<T, const N: usize> Array for [T; N]'
-impl <T, const N: usize> Array for [T; N] {
+// @has - '//*[@class="impl has-srclink"]' 'impl<T, const N: usize> Array for [T; N]'
+impl<T, const N: usize> Array for [T; N] {
     type Item = T;
 }

src/test/rustdoc/const-generics/const-generics-docs.rs

@@ -36,7 +36,7 @@ pub struct Foo<const N: usize> where u8: Trait<N>;
 // @has foo/struct.Bar.html '//pre[@class="rust struct"]' 'pub struct Bar<T, const N: usize>(_)'
 pub struct Bar<T, const N: usize>([T; N]);
 
-// @has foo/struct.Foo.html '//div[@id="impl"]/h3[@class="code-header in-band"]' 'impl<const M: usize> Foo<M> where u8: Trait<M>'
+// @has foo/struct.Foo.html '//*[@id="impl"]/h3[@class="code-header in-band"]' 'impl<const M: usize> Foo<M> where u8: Trait<M>'
 impl<const M: usize> Foo<M> where u8: Trait<M> {
     // @has - '//*[@id="associatedconstant.FOO_ASSOC"]' 'pub const FOO_ASSOC: usize'
     pub const FOO_ASSOC: usize = M + 13;
@@ -47,7 +47,7 @@ impl<const M: usize> Foo<M> where u8: Trait<M> {
     }
 }
 
-// @has foo/struct.Bar.html '//div[@id="impl"]/h3[@class="code-header in-band"]' 'impl<const M: usize> Bar<u8, M>'
+// @has foo/struct.Bar.html '//*[@id="impl"]/h3[@class="code-header in-band"]' 'impl<const M: usize> Bar<u8, M>'
 impl<const M: usize> Bar<u8, M> {
     // @has - '//*[@id="method.hey"]' \
     //      'pub fn hey<const N: usize>(&self) -> Foo<N> where u8: Trait<N>'

src/test/rustdoc/const-generics/const-impl.rs

@@ -1,7 +1,5 @@
 #![allow(incomplete_features)]
-
 #![feature(adt_const_params)]
-
 #![crate_name = "foo"]
 
 #[derive(PartialEq, Eq)]
@@ -11,20 +9,20 @@ pub enum Order {
 }
 
 // @has foo/struct.VSet.html '//pre[@class="rust struct"]' 'pub struct VSet<T, const ORDER: Order>'
-// @has foo/struct.VSet.html '//div[@id="impl-Send"]/h3[@class="code-header in-band"]' 'impl<T, const ORDER: Order> Send for VSet<T, ORDER>'
-// @has foo/struct.VSet.html '//div[@id="impl-Sync"]/h3[@class="code-header in-band"]' 'impl<T, const ORDER: Order> Sync for VSet<T, ORDER>'
+// @has foo/struct.VSet.html '//*[@id="impl-Send"]/h3[@class="code-header in-band"]' 'impl<T, const ORDER: Order> Send for VSet<T, ORDER>'
+// @has foo/struct.VSet.html '//*[@id="impl-Sync"]/h3[@class="code-header in-band"]' 'impl<T, const ORDER: Order> Sync for VSet<T, ORDER>'
 pub struct VSet<T, const ORDER: Order> {
     inner: Vec<T>,
 }
 
-// @has foo/struct.VSet.html '//div[@id="impl"]/h3[@class="code-header in-band"]' 'impl<T> VSet<T, { Order::Sorted }>'
+// @has foo/struct.VSet.html '//*[@id="impl"]/h3[@class="code-header in-band"]' 'impl<T> VSet<T, { Order::Sorted }>'
 impl<T> VSet<T, { Order::Sorted }> {
     pub fn new() -> Self {
         Self { inner: Vec::new() }
     }
 }
 
-// @has foo/struct.VSet.html '//div[@id="impl-1"]/h3[@class="code-header in-band"]' 'impl<T> VSet<T, { Order::Unsorted }>'
+// @has foo/struct.VSet.html '//*[@id="impl-1"]/h3[@class="code-header in-band"]' 'impl<T> VSet<T, { Order::Unsorted }>'
 impl<T> VSet<T, { Order::Unsorted }> {
     pub fn new() -> Self {
         Self { inner: Vec::new() }
@@ -33,7 +31,7 @@ impl<T> VSet<T, { Order::Unsorted }> {
 
 pub struct Escape<const S: &'static str>;
 
-// @has foo/struct.Escape.html '//div[@id="impl"]/h3[@class="code-header in-band"]' 'impl Escape<r#"<script>alert("Escape");</script>"#>'
+// @has foo/struct.Escape.html '//*[@id="impl"]/h3[@class="code-header in-band"]' 'impl Escape<r#"<script>alert("Escape");</script>"#>'
 impl Escape<r#"<script>alert("Escape");</script>"#> {
     pub fn f() {}
 }

src/test/rustdoc/empty-impls.rs

@@ -1,19 +1,19 @@
 #![crate_name = "foo"]
 
 // @has foo/struct.Foo.html
-// @has - '//div[@id="synthetic-implementations-list"]/div[@id="impl-Send"]' 'impl Send for Foo'
+// @has - '//div[@id="synthetic-implementations-list"]/*[@id="impl-Send"]' 'impl Send for Foo'
 pub struct Foo;
 
 pub trait EmptyTrait {}
 
-// @has - '//div[@id="trait-implementations-list"]/div[@id="impl-EmptyTrait"]' 'impl EmptyTrait for Foo'
+// @has - '//div[@id="trait-implementations-list"]/*[@id="impl-EmptyTrait"]' 'impl EmptyTrait for Foo'
 impl EmptyTrait for Foo {}
 
 pub trait NotEmpty {
     fn foo(&self);
 }
 
-// @has - '//div[@id="trait-implementations-list"]/details/summary/div[@id="impl-NotEmpty"]' 'impl NotEmpty for Foo'
+// @has - '//div[@id="trait-implementations-list"]/details/summary/*[@id="impl-NotEmpty"]' 'impl NotEmpty for Foo'
 impl NotEmpty for Foo {
     fn foo(&self) {}
 }

src/test/rustdoc/ensure-src-link.rs

@@ -2,5 +2,5 @@
 
 // This test ensures that the [src] link is present on traits items.
 
-// @has foo/trait.Iterator.html '//div[@id="method.zip"]//a[@class="srclink"]' "source"
+// @has foo/trait.Iterator.html '//*[@id="method.zip"]//a[@class="srclink"]' "source"
 pub use std::iter::Iterator;

src/test/rustdoc/extern-default-method.rs

@@ -4,6 +4,6 @@
 extern crate rustdoc_extern_default_method as ext;
 
 // @count extern_default_method/struct.Struct.html '//*[@id="method.provided"]' 1
-// @has extern_default_method/struct.Struct.html '//div[@id="method.provided"]//a[@class="fnname"]/@href' #method.provided
-// @has extern_default_method/struct.Struct.html '//div[@id="method.provided"]//a[@class="anchor"]/@href' #method.provided
+// @has extern_default_method/struct.Struct.html '//*[@id="method.provided"]//a[@class="fnname"]/@href' #method.provided
+// @has extern_default_method/struct.Struct.html '//*[@id="method.provided"]//a[@class="anchor"]/@href' #method.provided
 pub use ext::Struct;

src/test/rustdoc/generic-impl.rs

@@ -2,10 +2,10 @@
 
 use std::fmt;
 
-// @!has foo/struct.Bar.html '//div[@id="impl-ToString"]//h3[@class="code-header in-band"]' 'impl<T> ToString for T'
+// @!has foo/struct.Bar.html '//*[@id="impl-ToString"]//h3[@class="code-header in-band"]' 'impl<T> ToString for T'
 pub struct Bar;
 
-// @has foo/struct.Foo.html '//div[@id="impl-ToString"]//h3[@class="code-header in-band"]' 'impl<T> ToString for T'
+// @has foo/struct.Foo.html '//*[@id="impl-ToString"]//h3[@class="code-header in-band"]' 'impl<T> ToString for T'
 pub struct Foo;
 // @has foo/struct.Foo.html '//div[@class="sidebar-links"]/a[@href="#impl-ToString"]' 'ToString'
 

src/test/rustdoc/issue-29503.rs

@@ -5,12 +5,14 @@ pub trait MyTrait {
     fn my_string(&self) -> String;
 }
 
-// @has - "//div[@id='implementors-list']//div[@id='impl-MyTrait']//h3[@class='code-header in-band']" "impl<T> MyTrait for T where T: Debug"
-impl<T> MyTrait for T where T: fmt::Debug {
+// @has - "//div[@id='implementors-list']//*[@id='impl-MyTrait']//h3[@class='code-header in-band']" "impl<T> MyTrait for T where T: Debug"
+impl<T> MyTrait for T
+where
+    T: fmt::Debug,
+{
     fn my_string(&self) -> String {
         format!("{:?}", self)
     }
 }
 
-pub fn main() {
-}
+pub fn main() {}