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Auto merge of #76934 - camelid:rustdoc-allow-generic-params, r=jyn514

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Allow generic parameters in intra-doc links

Fixes #62834.

---

The contents of the generics will be mostly ignored (except for warning
if fully-qualified syntax is used, which is currently unsupported in
intra-doc links - see issue #74563).

* Allow links like `Vec<T>`, `Result<T, E>`, and `Option<Box<T>>`
* Allow links like `Vec::<T>::new()`
* Warn on
  * Unbalanced angle brackets (e.g. `Vec<T` or `Vec<T>>`)
  * Missing type to apply generics to (`<T>` or `<Box<T>>`)
  * Use of fully-qualified syntax (`<Vec as IntoIterator>::into_iter`)
  * Invalid path separator (`Vec:<T>:new`)
  * Too many angle brackets (`Vec<<T>>`)
  * Empty angle brackets (`Vec<>`)

Note that this implementation *does* allow some constructs that aren't
valid in the actual Rust syntax, for example `Box::<T>new()`. That may
not be supported in rustdoc in the future; it is an implementation
detail.
This commit is contained in:
bors 2020-10-10 21:19:50 +00:00
commit b1af43bc63
12 changed files with 441 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
compiler/rustc_middle/src/query/mod.rs
View File

@ -92,7 +92,7 @@ rustc_queries! {
/// Computes the `DefId` of the corresponding const parameter in case the `key` is a
/// const argument and returns `None` otherwise.
///
/// ```rust
/// ```ignore (incomplete)
/// let a = foo::<7>();
/// // ^ Calling `opt_const_param_of` for this argument,
///
@ -162,10 +162,12 @@ rustc_queries! {
/// Specifically this is the bounds written on the trait's type
/// definition, or those after the `impl` keyword
///
/// ```ignore (incomplete)
/// type X: Bound + 'lt
/// ^^^^^^^^^^^
/// // ^^^^^^^^^^^
/// impl Debug + Display
/// ^^^^^^^^^^^^^^^
/// // ^^^^^^^^^^^^^^^
/// ```
///
/// `key` is the `DefId` of the associated type or opaque type.
///
@ -176,18 +178,22 @@ rustc_queries! {
/// Elaborated version of the predicates from `explicit_item_bounds`.
///
/// Example for
/// For example:
///
/// ```
/// trait MyTrait {
/// type MyAType: Eq + ?Sized`
/// type MyAType: Eq + ?Sized;
/// }
/// ```
///
/// `explicit_item_bounds` returns `[<Self as MyTrait>::MyAType: Eq]`,
/// and `item_bounds` returns
/// ```text
/// [
/// <Self as Trait>::MyAType: Eq,
/// <Self as Trait>::MyAType: PartialEq<<Self as Trait>::MyAType>
/// ]
/// ```
///
/// Bounds from the parent (e.g. with nested impl trait) are not included.
query item_bounds(key: DefId) -> &'tcx ty::List<ty::Predicate<'tcx>> {

3
library/core/src/option.rs
View File

@ -141,6 +141,9 @@
//! ```
//!
//! [`Box<T>`]: ../../std/boxed/struct.Box.html
//! [`Box<U>`]: ../../std/boxed/struct.Box.html
//! [`num::NonZero*`]: crate::num
//! [`ptr::NonNull<U>`]: crate::ptr::NonNull
#![stable(feature = "rust1", since = "1.0.0")]

2
src/doc/rustdoc/src/SUMMARY.md
View File

@ -8,5 +8,5 @@
- [Linking to items by name](linking-to-items-by-name.md)
- [Lints](lints.md)
- [Passes](passes.md)
- [Advanced Features](advanced-features.md)
- [Advanced features](advanced-features.md)
- [Unstable features](unstable-features.md)

2
src/doc/rustdoc/src/advanced-features.md
View File

@ -1,4 +1,4 @@
# Advanced Features
# Advanced features
The features listed on this page fall outside the rest of the main categories.

41
src/doc/rustdoc/src/linking-to-items-by-name.md
View File

@ -1,6 +1,7 @@
# Linking to items by name
Rustdoc is capable of directly linking to other rustdoc pages in Markdown documentation using the path of item as a link.
Rustdoc is capable of directly linking to other rustdoc pages using the path of
the item as a link.
For example, in the following code all of the links will link to the rustdoc page for `Bar`:
@ -19,15 +20,26 @@ pub struct Foo3;
/// This struct is also not [`Bar`]
pub struct Foo4;
/// This struct *is* [`Bar`]!
pub struct Bar;
```
You can refer to anything in scope, and use paths, including `Self`, `self`, `super`, and `crate`. You may also use `foo()` and `foo!()` to refer to methods/functions and macros respectively. Backticks around the link will be stripped.
Backticks around the link will be stripped, so ``[`Option`]`` will correctly
link to `Option`.
You can refer to anything in scope, and use paths, including `Self`, `self`,
`super`, and `crate`. You may also use `foo()` and `foo!()` to refer to methods/functions and macros, respectively.
You can also refer to items with generic parameters like `Vec<T>`. The link will
resolve as if you had written ``[`Vec<T>`](Vec)``. Fully-qualified syntax (for example,
`<Vec as IntoIterator>::into_iter()`) is [not yet supported][fqs-issue], however.
[fqs-issue]: https://github.com/rust-lang/rust/issues/74563
```rust,edition2018
use std::sync::mpsc::Receiver;
/// This is an version of [`Receiver`], with support for [`std::future`].
/// This is a version of [`Receiver<T>`] with support for [`std::future`].
///
/// You can obtain a [`std::future::Future`] by calling [`Self::recv()`].
pub struct AsyncReceiver<T> {
@ -44,13 +56,15 @@ impl<T> AsyncReceiver<T> {
You can also link to sections using URL fragment specifiers:
```rust
/// This is a special implementation of [positional parameters]
/// This is a special implementation of [positional parameters].
///
/// [positional parameters]: std::fmt#formatting-parameters
struct MySpecialFormatter;
```
Paths in Rust have three namespaces: type, value, and macro. Items from these namespaces are allowed to overlap. In case of ambiguity, rustdoc will warn about the ambiguity and ask you to disambiguate, which can be done by using a prefix like `struct@`, `enum@`, `type@`, `trait@`, `union@`, `const@`, `static@`, `value@`, `function@`, `mod@`, `fn@`, `module@`, `method@`, `prim@`, `primitive@`, `macro@`, or `derive@`:
Paths in Rust have three namespaces: type, value, and macro. Item names must be
unique within their namespace, but can overlap with items outside of their
namespace. In case of ambiguity, rustdoc will warn about the ambiguity and ask you to disambiguate, which can be done by using a prefix like `struct@`, `enum@`, `type@`, `trait@`, `union@`, `const@`, `static@`, `value@`, `fn@`, `function@`, `mod@`, `module@`, `method@`, `prim@`, `primitive@`, `macro@`, or `derive@`:
```rust
/// See also: [`Foo`](struct@Foo)
@ -62,4 +76,19 @@ struct Foo {}
fn Foo() {}
```
Note: Because of how `macro_rules` macros are scoped in Rust, the intra-doc links of a `macro_rules` macro will be resolved relative to the crate root, as opposed to the module it is defined in.
You can also disambiguate for functions by adding `()` after the function name,
or for macros by adding `!` after the macro name:
```rust
/// See also: [`Foo`](struct@Foo)
struct Bar;
/// This is different from [`Foo()`]
struct Foo {}
fn Foo() {}
```
Note: Because of how `macro_rules!` macros are scoped in Rust, the intra-doc links of a `macro_rules!` macro will be resolved [relative to the crate root][#72243], as opposed to the module it is defined in.
[#72243]: https://github.com/rust-lang/rust/issues/72243

10
src/doc/rustdoc/src/lints.md
View File

@ -4,18 +4,18 @@
can use them like any other lints by doing this:
```rust,ignore
#![allow(missing_docs)] // allowing the lint, no message
#![warn(missing_docs)] // warn if there is missing docs
#![deny(missing_docs)] // rustdoc will fail if there is missing docs
#![allow(missing_docs)] // allows the lint, no diagnostics will be reported
#![warn(missing_docs)] // warn if there are missing docs
#![deny(missing_docs)] // error if there are missing docs
```
Here is the list of the lints provided by `rustdoc`:
## broken_intra_doc_links
This lint **warns by default**. This lint detects when an [intra-doc link] fails to get resolved. For example:
This lint **warns by default**. This lint detects when an [intra-doc link] fails to be resolved. For example:
[intra-doc link]: linking-to-items-by-name.html
[intra-doc link]: linking-to-items-by-name.md
```rust
/// I want to link to [`Nonexistent`] but it doesn't exist!

2
src/librustdoc/lib.rs
View File

@ -3,11 +3,13 @@
html_playground_url = "https://play.rust-lang.org/"
)]
#![feature(rustc_private)]
#![feature(array_methods)]
#![feature(box_patterns)]
#![feature(box_syntax)]
#![feature(in_band_lifetimes)]
#![feature(nll)]
#![feature(or_patterns)]
#![feature(peekable_next_if)]
#![feature(test)]
#![feature(crate_visibility_modifier)]
#![feature(never_type)]

203
src/librustdoc/passes/collect_intra_doc_links.rs
View File

@ -23,6 +23,7 @@ use smallvec::{smallvec, SmallVec};
use std::borrow::Cow;
use std::cell::Cell;
use std::mem;
use std::ops::Range;
use crate::clean::*;
@ -65,10 +66,53 @@ enum ResolutionFailure<'a> {
NotResolved { module_id: DefId, partial_res: Option<Res>, unresolved: Cow<'a, str> },
/// should not ever happen
NoParentItem,
/// This link has malformed generic parameters; e.g., the angle brackets are unbalanced.
MalformedGenerics(MalformedGenerics),
/// used to communicate that this should be ignored, but shouldn't be reported to the user
Dummy,
}
#[derive(Debug)]
enum MalformedGenerics {
/// This link has unbalanced angle brackets.
///
/// For example, `Vec<T` should trigger this, as should `Vec<T>>`.
UnbalancedAngleBrackets,
/// The generics are not attached to a type.
///
/// For example, `<T>` should trigger this.
///
/// This is detected by checking if the path is empty after the generics are stripped.
MissingType,
/// The link uses fully-qualified syntax, which is currently unsupported.
///
/// For example, `<Vec as IntoIterator>::into_iter` should trigger this.
///
/// This is detected by checking if ` as ` (the keyword `as` with spaces around it) is inside
/// angle brackets.
HasFullyQualifiedSyntax,
/// The link has an invalid path separator.
///
/// For example, `Vec:<T>:new()` should trigger this. Note that `Vec:new()` will **not**
/// trigger this because it has no generics and thus [`strip_generics_from_path`] will not be
/// called.
///
/// Note that this will also **not** be triggered if the invalid path separator is inside angle
/// brackets because rustdoc mostly ignores what's inside angle brackets (except for
/// [`HasFullyQualifiedSyntax`](MalformedGenerics::HasFullyQualifiedSyntax)).
///
/// This is detected by checking if there is a colon followed by a non-colon in the link.
InvalidPathSeparator,
/// The link has too many angle brackets.
///
/// For example, `Vec<<T>>` should trigger this.
TooManyAngleBrackets,
/// The link has empty angle brackets.
///
/// For example, `Vec<>` should trigger this.
EmptyAngleBrackets,
}
impl ResolutionFailure<'a> {
// This resolved fully (not just partially) but is erroneous for some other reason
fn full_res(&self) -> Option<Res> {
@ -908,6 +952,7 @@ impl LinkCollector<'_, '_> {
let link_text;
let mut path_str;
let disambiguator;
let stripped_path_string;
let (mut res, mut fragment) = {
path_str = if let Ok((d, path)) = Disambiguator::from_str(&link) {
disambiguator = Some(d);
@ -918,7 +963,7 @@ impl LinkCollector<'_, '_> {
}
.trim();
if path_str.contains(|ch: char| !(ch.is_alphanumeric() || ch == ':' || ch == '_')) {
if path_str.contains(|ch: char| !(ch.is_alphanumeric() || ":_<>, ".contains(ch))) {
return None;
}
@ -981,6 +1026,36 @@ impl LinkCollector<'_, '_> {
module_id = DefId { krate, index: CRATE_DEF_INDEX };
}
// Strip generics from the path.
if path_str.contains(['<', '>'].as_slice()) {
stripped_path_string = match strip_generics_from_path(path_str) {
Ok(path) => path,
Err(err_kind) => {
debug!("link has malformed generics: {}", path_str);
resolution_failure(
self,
&item,
path_str,
disambiguator,
dox,
link_range,
smallvec![err_kind],
);
return None;
}
};
path_str = &stripped_path_string;
}
// Sanity check to make sure we don't have any angle brackets after stripping generics.
assert!(!path_str.contains(['<', '>'].as_slice()));
// The link is not an intra-doc link if it still contains commas or spaces after
// stripping generics.
if path_str.contains([',', ' '].as_slice()) {
return None;
}
match self.resolve_with_disambiguator(
disambiguator,
item,
@ -1714,6 +1789,27 @@ fn resolution_failure(
diag.level = rustc_errors::Level::Bug;
"all intra doc links should have a parent item".to_owned()
}
ResolutionFailure::MalformedGenerics(variant) => match variant {
MalformedGenerics::UnbalancedAngleBrackets => {
String::from("unbalanced angle brackets")
}
MalformedGenerics::MissingType => {
String::from("missing type for generic parameters")
}
MalformedGenerics::HasFullyQualifiedSyntax => {
diag.note("see https://github.com/rust-lang/rust/issues/74563 for more information");
String::from("fully-qualified syntax is unsupported")
}
MalformedGenerics::InvalidPathSeparator => {
String::from("has invalid path separator")
}
MalformedGenerics::TooManyAngleBrackets => {
String::from("too many angle brackets")
}
MalformedGenerics::EmptyAngleBrackets => {
String::from("empty angle brackets")
}
},
};
if let Some(span) = sp {
diag.span_label(span, &note);
@ -1904,3 +2000,108 @@ fn is_primitive(path_str: &str, ns: Namespace) -> Option<(&'static str, Res)> {
fn primitive_impl(cx: &DocContext<'_>, path_str: &str) -> Option<&'static SmallVec<[DefId; 4]>> {
Some(PrimitiveType::from_symbol(Symbol::intern(path_str))?.impls(cx.tcx))
}
fn strip_generics_from_path(path_str: &str) -> Result<String, ResolutionFailure<'static>> {
let mut stripped_segments = vec![];
let mut path = path_str.chars().peekable();
let mut segment = Vec::new();
while let Some(chr) = path.next() {
match chr {
':' => {
if path.next_if_eq(&':').is_some() {
let stripped_segment =
strip_generics_from_path_segment(mem::take(&mut segment))?;
if !stripped_segment.is_empty() {
stripped_segments.push(stripped_segment);
}
} else {
return Err(ResolutionFailure::MalformedGenerics(
MalformedGenerics::InvalidPathSeparator,
));
}
}
'<' => {
segment.push(chr);
match path.next() {
Some('<') => {
return Err(ResolutionFailure::MalformedGenerics(
MalformedGenerics::TooManyAngleBrackets,
));
}
Some('>') => {
return Err(ResolutionFailure::MalformedGenerics(
MalformedGenerics::EmptyAngleBrackets,
));
}
Some(chr) => {
segment.push(chr);
while let Some(chr) = path.next_if(|c| *c != '>') {
segment.push(chr);
}
}
None => break,
}
}
_ => segment.push(chr),
}
debug!("raw segment: {:?}", segment);
}
if !segment.is_empty() {
let stripped_segment = strip_generics_from_path_segment(segment)?;
if !stripped_segment.is_empty() {
stripped_segments.push(stripped_segment);
}
}
debug!("path_str: {:?}\nstripped segments: {:?}", path_str, &stripped_segments);
let stripped_path = stripped_segments.join("::");
if !stripped_path.is_empty() {
Ok(stripped_path)
} else {
Err(ResolutionFailure::MalformedGenerics(MalformedGenerics::MissingType))
}
}
fn strip_generics_from_path_segment(
segment: Vec<char>,
) -> Result<String, ResolutionFailure<'static>> {
let mut stripped_segment = String::new();
let mut param_depth = 0;
let mut latest_generics_chunk = String::new();
for c in segment {
if c == '<' {
param_depth += 1;
latest_generics_chunk.clear();
} else if c == '>' {
param_depth -= 1;
if latest_generics_chunk.contains(" as ") {
// The segment tries to use fully-qualified syntax, which is currently unsupported.
// Give a helpful error message instead of completely ignoring the angle brackets.
return Err(ResolutionFailure::MalformedGenerics(
MalformedGenerics::HasFullyQualifiedSyntax,
));
}
} else {
if param_depth == 0 {
stripped_segment.push(c);
} else {
latest_generics_chunk.push(c);
}
}
}
if param_depth == 0 {
Ok(stripped_segment)
} else {
// The segment has unbalanced angle brackets, e.g. `Vec<T` or `Vec<T>>`
Err(ResolutionFailure::MalformedGenerics(MalformedGenerics::UnbalancedAngleBrackets))
}
}

2
src/test/rustdoc-ui/intra-link-errors.rs
View File

@ -2,7 +2,7 @@
//~^ NOTE lint level is defined
// FIXME: this should say that it was skipped (maybe an allowed by default lint?)
/// [<invalid syntax>]
/// [invalid intra-doc syntax!!]
/// [path::to::nonexistent::module]
//~^ ERROR unresolved link

19
src/test/rustdoc-ui/intra-link-malformed-generics.rs Normal file
View File

@ -0,0 +1,19 @@
#![deny(broken_intra_doc_links)]
//! [Vec<] //~ ERROR
//! [Vec<Box<T] //~ ERROR
//! [Vec<Box<T>] //~ ERROR
//! [Vec<Box<T>>>] //~ ERROR
//! [Vec<T>>>] //~ ERROR
//! [<Vec] //~ ERROR
//! [Vec::<] //~ ERROR
//! [<T>] //~ ERROR
//! [<invalid syntax>] //~ ERROR
//! [Vec:<T>:new()] //~ ERROR
//! [Vec<<T>>] //~ ERROR
//! [Vec<>] //~ ERROR
//! [Vec<<>>] //~ ERROR
// FIXME(#74563) support UFCS
//! [<Vec as IntoIterator>::into_iter] //~ ERROR
//! [<Vec<T> as IntoIterator>::iter] //~ ERROR

102
src/test/rustdoc-ui/intra-link-malformed-generics.stderr Normal file
View File

@ -0,0 +1,102 @@
error: unresolved link to `Vec<`
--> $DIR/intra-link-malformed-generics.rs:3:6
|
LL | //! [Vec<]
| ^^^^ unbalanced angle brackets
|
note: the lint level is defined here
--> $DIR/intra-link-malformed-generics.rs:1:9
|
LL | #![deny(broken_intra_doc_links)]
| ^^^^^^^^^^^^^^^^^^^^^^
error: unresolved link to `Vec<Box<T`
--> $DIR/intra-link-malformed-generics.rs:4:6
|
LL | //! [Vec<Box<T]
| ^^^^^^^^^ unbalanced angle brackets
error: unresolved link to `Vec<Box<T>`
--> $DIR/intra-link-malformed-generics.rs:5:6
|
LL | //! [Vec<Box<T>]
| ^^^^^^^^^^ unbalanced angle brackets
error: unresolved link to `Vec<Box<T>>>`
--> $DIR/intra-link-malformed-generics.rs:6:6
|
LL | //! [Vec<Box<T>>>]
| ^^^^^^^^^^^^ unbalanced angle brackets
error: unresolved link to `Vec<T>>>`
--> $DIR/intra-link-malformed-generics.rs:7:6
|
LL | //! [Vec<T>>>]
| ^^^^^^^^ unbalanced angle brackets
error: unresolved link to `<Vec`
--> $DIR/intra-link-malformed-generics.rs:8:6
|
LL | //! [<Vec]
| ^^^^ unbalanced angle brackets
error: unresolved link to `Vec::<`
--> $DIR/intra-link-malformed-generics.rs:9:6
|
LL | //! [Vec::<]
| ^^^^^^ unbalanced angle brackets
error: unresolved link to `<T>`
--> $DIR/intra-link-malformed-generics.rs:10:6
|
LL | //! [<T>]
| ^^^ missing type for generic parameters
error: unresolved link to `<invalid syntax>`
--> $DIR/intra-link-malformed-generics.rs:11:6
|
LL | //! [<invalid syntax>]
| ^^^^^^^^^^^^^^^^ missing type for generic parameters
error: unresolved link to `Vec:<T>:new`
--> $DIR/intra-link-malformed-generics.rs:12:6
|
LL | //! [Vec:<T>:new()]
| ^^^^^^^^^^^^^ has invalid path separator
error: unresolved link to `Vec<<T>>`
--> $DIR/intra-link-malformed-generics.rs:13:6
|
LL | //! [Vec<<T>>]
| ^^^^^^^^ too many angle brackets
error: unresolved link to `Vec<>`
--> $DIR/intra-link-malformed-generics.rs:14:6
|
LL | //! [Vec<>]
| ^^^^^ empty angle brackets
error: unresolved link to `Vec<<>>`
--> $DIR/intra-link-malformed-generics.rs:15:6
|
LL | //! [Vec<<>>]
| ^^^^^^^ too many angle brackets
error: unresolved link to `<Vec as IntoIterator>::into_iter`
--> $DIR/intra-link-malformed-generics.rs:18:6
|
LL | //! [<Vec as IntoIterator>::into_iter]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ fully-qualified syntax is unsupported
|
= note: see https://github.com/rust-lang/rust/issues/74563 for more information
error: unresolved link to `<Vec<T> as IntoIterator>::iter`
--> $DIR/intra-link-malformed-generics.rs:19:6
|
LL | //! [<Vec<T> as IntoIterator>::iter]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ fully-qualified syntax is unsupported
|
= note: see https://github.com/rust-lang/rust/issues/74563 for more information
error: aborting due to 15 previous errors

59
src/test/rustdoc/intra-doc-link-generic-params.rs Normal file
View File

@ -0,0 +1,59 @@
// ignore-tidy-linelength
#![crate_name = "foo"]
//! Here's a link to [`Vec<T>`] and one to [`Box<Vec<Option<T>>>`].
//! Here's a link to [`Iterator<Box<T>>::Item`].
//!
// @has foo/index.html '//a[@href="https://doc.rust-lang.org/nightly/alloc/vec/struct.Vec.html"]' 'Vec<T>'
// @has foo/index.html '//a[@href="https://doc.rust-lang.org/nightly/alloc/boxed/struct.Box.html"]' 'Box<Vec<Option<T>>>'
// @has foo/index.html '//a[@href="https://doc.rust-lang.org/nightly/core/iter/traits/iterator/trait.Iterator.html#associatedtype.Item"]' 'Iterator<Box<T>>::Item'
//! And what about a link to [just `Option`](Option) and, [with the generic, `Option<T>`](Option<T>)?
//!
// @has foo/index.html '//a[@href="https://doc.rust-lang.org/nightly/core/option/enum.Option.html"]' 'just Option'
// @has foo/index.html '//a[@href="https://doc.rust-lang.org/nightly/core/option/enum.Option.html"]' 'with the generic, Option<T>'
//! We should also try linking to [`Result<T, E>`]; it has *two* generics!
//!
// @has foo/index.html '//a[@href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html"]' 'Result<T, E>'
//! Now let's test a trickier case: [`Vec::<T>::new`], or you could write it
//! [with parentheses as `Vec::<T>::new()`][Vec::<T>::new()].
//! And what about something even harder? That would be [`Vec::<Box<T>>::new()`].
//!
// @has foo/index.html '//a[@href="https://doc.rust-lang.org/nightly/alloc/vec/struct.Vec.html#method.new"]' 'Vec::<T>::new'
// @has foo/index.html '//a[@href="https://doc.rust-lang.org/nightly/alloc/vec/struct.Vec.html#method.new"]' 'with parentheses as Vec::<T>::new()'
// @has foo/index.html '//a[@href="https://doc.rust-lang.org/nightly/alloc/vec/struct.Vec.html#method.new"]' 'Vec::<Box<T>>::new()'
//! This is also pretty tricky: [`TypeId::of::<String>()`].
//! And this too: [`Vec::<std::error::Error>::len`].
//!
// @has foo/index.html '//a[@href="https://doc.rust-lang.org/nightly/core/any/struct.TypeId.html#method.of"]' 'TypeId::of::<String>()'
// @has foo/index.html '//a[@href="https://doc.rust-lang.org/nightly/alloc/vec/struct.Vec.html#method.len"]' 'Vec::<std::error::Error>::len'
//! We unofficially and implicitly support things that aren't valid in the actual Rust syntax, like
//! [`Box::<T>new()`]. We may not support them in the future!
//!
// @has foo/index.html '//a[@href="https://doc.rust-lang.org/nightly/alloc/boxed/struct.Box.html#method.new"]' 'Box::<T>new()'
//! These will be resolved as regular links:
//! - [`this is <invalid syntax> first`](https://www.rust-lang.org)
//! - [`this is <invalid syntax> twice`]
//! - [`<invalid syntax> thrice`](https://www.rust-lang.org)
//! - [`<invalid syntax> four times`][rlo]
//! - [a < b][rlo]
//! - [c > d]
//!
//! [`this is <invalid syntax> twice`]: https://www.rust-lang.org
//! [rlo]: https://www.rust-lang.org
//! [c > d]: https://www.rust-lang.org
//!
// @has foo/index.html '//a[@href="https://www.rust-lang.org"]' 'this is <invalid syntax> first'
// @has foo/index.html '//a[@href="https://www.rust-lang.org"]' 'this is <invalid syntax> twice'
// @has foo/index.html '//a[@href="https://www.rust-lang.org"]' '<invalid syntax> thrice'
// @has foo/index.html '//a[@href="https://www.rust-lang.org"]' '<invalid syntax> four times'
// @has foo/index.html '//a[@href="https://www.rust-lang.org"]' 'a < b'
// @has foo/index.html '//a[@href="https://www.rust-lang.org"]' 'c > d'
use std::any::TypeId;