The paragraph described a case where we can't optimize away repetitive
dynamic stack allocation. However, as arielb1 pointed out, it can
actually optimizable by dynamically delaying the stack unwinding.
Use #[non_exhaustive] on internal enums
This replaces `__Nonexhaustive` variants (and variants thereof) with `#[non_exhaustive]`. These were mostly unstable previously, with the exception of the `cloudabi` enums and `Level` in proc_macro: these were `#[doc(hidden)]`, so clearly intended not to be used directly. It should be safe to replace all of these.
This commit stabilizes some of the `proc_macro` language feature as well as a
number of APIs in the `proc_macro` crate as [previously discussed][1]. This
means that on stable Rust you can now define custom procedural macros which
operate as attributes attached to items or `macro_rules!`-like bang-style
invocations. This extends the suite of currently stable procedural macros,
custom derives, with custom attributes and custom bang macros.
Note though that despite the stabilization in this commit procedural macros are
still not usable on stable Rust. To stabilize that we'll need to stabilize at
least part of the `use_extern_macros` feature. Currently you can define a
procedural macro attribute but you can't import it to call it!
A summary of the changes made in this PR (as well as the various consequences)
is:
* The `proc_macro` language and library features are now stable.
* Other APIs not stabilized in the `proc_macro` crate are now named under a
different feature, such as `proc_macro_diagnostic` or `proc_macro_span`.
* A few checks in resolution for `proc_macro` being enabled have switched over
to `use_extern_macros` being enabled. This means that code using
`#![feature(proc_macro)]` today will likely need to move to
`#![feature(use_extern_macros)]`.
It's intended that this PR, once landed, will be followed up with an attempt to
stabilize a small slice of `use_extern_macros` just for procedural macros to
make this feature 100% usable on stable.
[1]: https://internals.rust-lang.org/t/help-stabilize-a-subset-of-macros-2-0/7252
rustdoc codeblock hash escape
So that docstring text such as the following (in a code block) can be created ergonomically:
```rust
let s = "
foo
# bar
baz
";
```
Such code in a docstring hide the <code> # bar</code> line.
Previously, using two consecutive hashes <code> ## bar</code> would turn the line into _shown_ `# bar`, losing the leading whitespace. A line of code like <code> # bar</code> (such as in the example above) **could not be represented** in the docstring text.
This commit makes the two consecutive hashes not also trim the leading whitespace — the two hashes simply **escape** into a single hash and do not hide the line, leaving the rest of that line unaffected. The new docstring text to achieve the above code block is:
```rust
/// ```
/// let s = "
/// foo
/// ## bar
/// baz
/// ";
/// ```
```
Mention spec and indented blocks in doctest docs
Fixes#49717.
This commit adds a new section to the Documentation Test docs, which briefly mentions indented code blocks, and links to the CommonMark specification for both.
I’m not sure about saying "fenced code blocks the more popular choice in the Rust community” because it seems like I’m speaking for everyone, but I can’t think of a better way to phrase it!
Update rustdoc book to suggest using Termination trait instead of hidden ‘foo’ function
Closes#50721.
I suggest that someone double-checks my English since I am not a native speaker.
r? @steveklabnik
Add doc comment to hiding portions of code example
fixes#50816
Not sure if this is all that's needed, but I think it's a good start. One thing to note is that the code block is a text block where it could possibly be a rust block.
