This introduces a new lint that aims to check for missing terminal
punctuation in doc comments.
## Lint scope and motivation
It partially addresses
https://github.com/rust-lang/rust-clippy/issues/8371 by currently
focusing on the case that is both the easiest to look for without
advanced NLP capacities and still very useful: missing punctuation at
the end of the last sentence of doc comments. This is particularly
useful when working in a team to enforce a style guide and make sure all
doc comments end with some kind of punctuation, which is often forgotten
in the case of short, single-sentence doc comments. The lint is biased
towards avoiding false positives so it can be easily adopted without
requiring an excessive number of `#[expect]` attributes.
It is currently only concerned with Latin languages, but adding support
for `。` for instance should be very easy.
Even if consistently ending doc comments (even very short ones) with
punctuation is somewhat of an opinion, it seems sufficiently
well-established, [at least in the
`std`](https://github.com/rust-lang/rust/pull/91886), to warrant its own
lint, even if of course it would be allow-by-default.
## Lint category and possible evolution
Because it is unclear how useful and more complex it would be to also
look for missing punctuation at the end of *each* Markdown paragraphs, I
opted for the `nursery` category for now. My understanding of [the
stability
guarantees](https://github.com/rust-lang/rfcs/blob/master/text/2476-clippy-uno.md#stability-guarantees)
is that would it not be acceptable to add such capability later if it
was part of `pedantic` or `restriction` categories right away. I tried
to make sure the lint name allows this kind of iterative evolution.
## Testing
I ran the lint against the `core` library which led me to introduce a
few special cases (which seem common enough) to avoid false positives:
e.g., the last sentence being in parentheses. After excluding specific
modules which should likely be excluded (e.g., `core_arch`,
`intrinsincs`), it currently finds a bit more than 200 errors in the
`core` library.
This lint also helped find issues with a few doc comments, which [are
now fixed](https://github.com/rust-lang/rust/pull/146136).
## How to review this PR
I suppose it is easier to have a look at the UI tests first before
checking the implementation.
---
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internal only changes)*
changelog: add new lint [`doc_paragraphs_missing_punctuation`]
86e036af36