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We don't currently apply automatic formatting to doc comment code blocks. As a
result, it has built up various idiosyncracies, which make such automatic
formatting difficult. Some of those idiosyncracies also make things harder for
human readers or other tools.

This PR makes a few improvements to doc code formatting, in the hopes of making
future automatic formatting easier, as well as in many cases providing net
readability improvements.

I would suggest reading each commit separately, as each commit contains one
class of changes.

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rustbot commented Jul 26, 2025

r? @ibraheemdev

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@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jul 26, 2025
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This error didn't show up in local testing. Investigating.

These examples feature Rust code that's presented primarily to
illustrate how its compilation would be handled, and these examples are
formatted to highlight those aspects in ways that rustfmt wouldn't
preserve. Turn formatting off in those examples.

(Doc code isn't formatted yet, but this will make it easier to enable
doc code formatting in the future.)
Because doc code does not get automatically formatted, some doc code has
creative placements of comments that automatic formatting can't handle.
Reformat those comments to make the resulting code support standard Rust
formatting without breaking; this is generally an improvement to
readability as well.

Some comments are not indented to the prevailing indent, and are instead
aligned under some bit of code. Indent them to the prevailing indent,
and put spaces *inside* the comments to align them with code.

Some comments span several lines of code (which aren't the line the
comment is about) and expect alignment. Reformat them into one comment
not broken up by unrelated intervening code.

Some comments are placed on the same line as an opening brace, placing
them effectively inside the subsequent block, such that formatting would
typically format them like a line of that block. Move those comments to
attach them to what they apply to.

Some comments are placed on the same line as a one-line braced block,
effectively attaching them to the closing brace, even though they're
about the code inside the block. Reformat to make sure the comment will
stay on the same line as the code it's commenting.
This leads tools like rustfmt to get confused, because the doc code
block effectively spans two doc comments. As a result, the tools think
the first code block is unclosed, and the subsequent terminator opens a
new block.

Move the FIXME comments outside the doc code blocks, instead.
This makes it easier for humans to parse, and improves the result of
potential future automatic formatting.
Placing the opening triple-backquote inside a `cfg_attr` makes many
tools confused, including syntax highlighters (e.g. vim's) and rustfmt.

Instead, use a `cfg` inside the doc code block.
@joshtriplett joshtriplett force-pushed the doc-code-formatting-prep branch from 175fa91 to 1e2d587 Compare July 26, 2025 05:14
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