Use details tag for trait implementors.
Part of #83332 and following on from #83337 and #83355.
This removes one category of JS-generated toggles (implementors), and replaces them with a `<details>` tag. This simplifies the JS, and fixes some bugs where things that were supposed to be hidden by the toggle were not hidden. Compare https://hoffman-andrews.com/rust/details-implementors/std/io/trait.Read.html#impl-Read vs https://doc.rust-lang.org/nightly/std/io/trait.Read.html#implementors.
This introduces a `left: -23px` to put the toggle in the correct place, matching the current style for `.collapse-toggle`.
It's worth noting this introduces a slight behavior change: since the entire line is now a `<summary>`, any part of the line is clickable. So for instance, in `impl Read for File`, clicking `impl` or `for` will collapse / expand the docs. Clicking `Read` or `File` still links to the appropriate documentation as before.
rustdoc: Convert sub-variant toggle to HTML
Instead of creating a JS toggle, this injects details/summary for
sub-variants of enums. This also fixes the CSS so that the toggle button
does not jump when expanding/collapsing.
Takes inspiration from #83337 and should be considered part of #83332. Not quite sure if the `.sub-variant` selectors could be further simplified? AFAICS it is only used in that place, and that does not seem to allow any recursion.
rustdoc: Remove most fields from ExternalCrate
Once https://github.com/rust-lang/rust/issues/84304 is fixed, I can get rid of ExternCrate altogether in favor of CrateNum, but in the meantime, this shrinks ExternalCrate quite a lot.
This might hurt compile-times; if it does, I can add `primitive` and `keyword` queries. I expect this to improve compilemem.
Helps with https://github.com/rust-lang/rust/issues/76382.
r? GuillaumeGomez
rustdoc: Hide `#text` in doc-tests
Since `#![attr]` and `#[attr]` are the only valid syntax that start with `#`, we can just special case those two tokens.
Fixes https://github.com/rust-lang/rust/issues/83284.
This makes Rustdoc titles for items read like
"x in cratename::blah::foo - Rust". Title for modules and other
non-items are unchanged, and still read like
"doccratenameconst::blah::foo - Rust". This makes managing several open
Rustdoc tabs easier.
Closes#84371.
rustdoc: Simplify some document functions
* Remove `prefix` param of `document_short/full`, `render_markdown`, as its always an empty string.
* Remove `Option` wrapping of `document_short` `parent`, as its always `Some`.
rustdoc: Show nag box on IE11
Rustdoc doesn't work on IE11. It's been broken for months, it isn't supported by the [tiered browser support list], it's even more severely broken on other Rust websites, and IE11 doesn't support the `<details>` tag that we want to use.
In the interest of honesty, let's give an actual error message for anyone on IE11.
[tiered browser support list]: https://github.com/rust-lang/rfcs/blob/master/text/1985-tiered-browser-support.md
* Remove `prefix` param of `document_short/full`, `render_markdown`, as its always an empty string.
* Remove `Option` wrapping of `document_short` `parent`, as its always `Some`.
Rustdoc doesn't work on IE11. It's been broken for months, it isn't supported
by the [tiered browser support list], it's even more severely broken on other
Rust websites, and IE11 doesn't support the `<details>` tag that we want
to use.
In the interest of honesty, let's give an actual error message for anyone
on IE11.
[tiered browser support list]: https://github.com/rust-lang/rfcs/blob/master/text/1985-tiered-browser-support.md
Remove unused footer section
I realized yesterday while working on docs.rs that rustdoc was generating a "footer"section that it doesn't use. No need to keep it then.
r? `@jyn514`
Instead of creating a JS toggle, this injects details/summary for
sub-variants of enums. This also fixes the CSS so that the toggle button
does not jump when expanding/collapsing.
rustdoc: Reduce visual weight of attributes.
Followup from #83337. As part of that PR, we stopped hiding attributes behind a toggle, because most things have just zero or one attributes. However, this made clear that the current rendering of attributes emphasizes them a lot, which distracts from function signatures. This PR changes their color of attributes to be the same as the toggles, and reduces their font weight.
This also removes `#[lang]` from the list of ALLOWED_ATTRIBUTES. This attribute is an implementation detail rather than part of the public-facing documentation.

Demo at https://hoffman-andrews.com/rust/de-emph-attr/std/string/struct.String.html#method.trim
rustdoc: move some search code into search.js
This reduces main.s from 3094 lines to 1587. Also it saves some bytes
of download in the case where search isn't used.
There were a fair number of variables that needed to be accessible in
both main.js and search.js, but I didn't want to put too many symbols in
the global namespace, so I consolidated much of the search-related
state and functions into a new object `window.searchState`.
Demo at https://hoffman-andrews.com/rust/move-search/std/?search=foo
Instead of using a depth counter and adding "../" to get to the top,
this commit makes rustdoc actually compare the path of what it's
linking from to the path that it's linking to. This makes the resulting
HTML shorter.
Here's a comparison of one of the largest (non-source) files in the
Rust standard library docs (about 4% improvement before gzipping).
$ wc -c struct.Wrapping.old.html struct.Wrapping.new.html
2387389 struct.Wrapping.old.html
2298538 struct.Wrapping.new.html
Most if it can be efficiently gzipped away.
$ wc -c struct.Wrapping.old.html.gz struct.Wrapping.new.html.gz
70679 struct.Wrapping.old.html.gz
70050 struct.Wrapping.new.html.gz
But it also makes a difference in the final DOM size, reducing it from 91MiB to 82MiB.
rustdoc: get rid of unused path printing code
The code for printing a raw path is only used in utils.rs, which only prints the alternative (non-HTML) format. Path has
a function that does the same thing without HTML support, so use that instead.
rustdoc: clean up and test macro visibility print
This fixes the overly-complex invariant mentioned in <https://github.com/rust-lang/rust/pull/83237#issuecomment-815346570>, where the macro source can't have any links in it only because the cache hasn't been populated yet.
The code for printing a raw path is only used in utils.rs,
which only prints the alternative (non-HTML) format. Path has
a function that does the same thing without HTML support,
so use that instead.