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bors 6d53018e85 Auto merge of #116471 - notriddle:notriddle/js-trait-alias, r=GuillaumeGomez
rustdoc: use JS to inline target type impl docs into alias

Preview docs:

- https://notriddle.com/rustdoc-html-demo-5/js-trait-alias/std/io/type.Result.html

- https://notriddle.com/rustdoc-html-demo-5/js-trait-alias-compiler/rustc_middle/ty/type.PolyTraitRef.html

This pull request also includes a bug fix for trait alias inlining across crates. This means more documentation is generated, and is why ripgrep runs slower (it's a thin wrapper on top of the `grep` crate, so 5% of its docs are now the Result type).

- Before, built with rustdoc 1.75.0-nightly (aa1a71e9e 2023-10-26), Result type alias method docs are missing: http://notriddle.com/rustdoc-html-demo-5/ripgrep-js-nightly/rg/type.Result.html
- After, built with this branch, all the methods on Result are shown: http://notriddle.com/rustdoc-html-demo-5/ripgrep-js-trait-alias/rg/type.Result.html

*Review note: This is mostly just reverting https://github.com/rust-lang/rust/pull/115201. The last commit has the new work in it.*

Fixes #115718

This is an attempt to balance three problems, each of which would
be violated by a simpler implementation:

- A type alias should show all the `impl` blocks for the target
  type, and vice versa, if they're applicable. If nothing was
  done, and rustdoc continues to match them up in HIR, this
  would not work.

- Copying the target type's docs into its aliases' HTML pages
  directly causes far too much redundant HTML text to be generated
  when a crate has large numbers of methods and large numbers
  of type aliases.

- Using JavaScript exclusively for type alias impl docs would
  be a functional regression, and could make some docs very hard
  to find for non-JS readers.

- Making sure that only applicable docs are show in the
  resulting page requires a type checkers. Do not reimplement
  the type checker in JavaScript.

So, to make it work, rustdoc stashes these type-alias-inlined docs
in a JSONP "database-lite". The file is generated in `write_shared.rs`,
included in a `<script>` tag added in `print_item.rs`, and `main.js`
takes care of patching the additional docs into the DOM.

The format of `trait.impl` and `type.impl` JS files are superficially
similar. Each line, except the JSONP wrapper itself, belongs to a crate,
and they are otherwise separate (rustdoc should be idempotent). The
"meat" of the file is HTML strings, so the frontend code is very simple.
Links are relative to the doc root, though, so the frontend needs to fix
that up, and inlined docs can reuse these files.

However, there are a few differences, caused by the sophisticated
features that type aliases have. Consider this crate graph:

```text
 ---------------------------------
 | crate A: struct Foo<T>        |
 |          type Bar = Foo<i32>  |
 |          impl X for Foo<i8>   |
 |          impl Y for Foo<i32>  |
 ---------------------------------
     |
 ----------------------------------
 | crate B: type Baz = A::Foo<i8> |
 |          type Xyy = A::Foo<i8> |
 |          impl Z for Xyy        |
 ----------------------------------
```

The type.impl/A/struct.Foo.js JS file has a structure kinda like this:

```js
JSONP({
"A": [["impl Y for Foo<i32>", "Y", "A::Bar"]],
"B": [["impl X for Foo<i8>", "X", "B::Baz", "B::Xyy"], ["impl Z for Xyy", "Z", "B::Baz"]],
});
```

When the type.impl file is loaded, only the current crate's docs are
actually used. The main reason to bundle them together is that there's
enough duplication in them for DEFLATE to remove the redundancy.

The contents of a crate are a list of impl blocks, themselves
represented as lists. The first item in the sublist is the HTML block,
the second item is the name of the trait (which goes in the sidebar),
and all others are the names of type aliases that successfully match.

This way:

- There's no need to generate these files for types that have no aliases
  in the current crate. If a dependent crate makes a type alias, it'll
  take care of generating its own docs.
- There's no need to reimplement parts of the type checker in
  JavaScript. The Rust backend does the checking, and includes its
  results in the file.
- Docs defined directly on the type alias are dropped directly in the
  HTML by `render_assoc_items`, and are accessible without JavaScript.
  The JSONP file will not list impl items that are known to be part
  of the main HTML file already.

[JSONP]: https://en.wikipedia.org/wiki/JSONP
2023-10-27 23:08:24 +00:00
.cargo Less once_cell more std 2023-09-01 17:30:59 +02:00
.github Add hyper-0.14.18 to metrics 2023-09-03 11:39:29 +02:00
.vscode Spelling 2023-04-19 09:45:55 -04:00
assets Automatically change text color in logo based on dark mode 2022-03-06 23:06:53 +11:00
bench_data Spelling 2023-04-19 09:45:55 -04:00
crates use visibility to check unused imports and delete some stmts 2023-10-22 21:27:46 +08:00
docs Resolve inlay hint data 2023-09-02 18:28:35 +03:00
editors/code fmt 2023-09-05 15:45:52 -04:00
lib internal: unpin serde 2023-08-21 14:29:18 +01:00
xtask Add hyper-0.14.18 to metrics 2023-09-03 11:39:29 +02:00
.editorconfig Set .editorconfig default indent size to 4 2023-07-11 23:02:54 +09:00
.git-blame-ignore-revs add prettier format commit to ignored revisions 2022-05-17 18:15:51 +01:00
.gitattributes Fix .gitattributes for test_data 2022-07-24 14:05:35 +02:00
.gitignore internal: add "Shuffle Crate Graph" command 2021-12-07 16:37:19 +01:00
Cargo.lock Replace format-args parser with upstream fork 2023-09-07 11:37:59 +02:00
Cargo.toml Replace format-args parser with upstream fork 2023-09-07 11:37:59 +02:00
LICENSE-APACHE Licenses 2018-01-10 22:47:04 +03:00
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README.md Fix r-a spelling in some places 2022-08-01 13:47:09 +02:00
rustfmt.toml Remove forcing \n via rustfmt 2019-11-02 22:19:59 +03:00
triagebot.toml Add triagebot no-merges config 2023-07-30 14:02:03 +02:00

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