rustdoc: Tracking issue for generating macro expansions on source code pages

[fmease]

This is a tracking issue for generating macro expansions on source code pages.
The feature can be enabled by passing --generate-macro-expansion -Zunstable-options to a nightly rustdoc.

Note

Tracking issues are used to record the overall progress of implementation.
They are also used as hubs connecting to other relevant issues, e.g., bugs or open design questions.

A tracking issue is however not meant for large scale discussion, questions, or bug reports.
Instead, open a dedicated issue for the specific matter or post in the #t-rustdoc Zulip channel.

Discussion comments will get marked as off-topic or deleted.
Repeated discussions on the tracking issue may lead to the tracking issue getting locked.

Steps

• Implementation PR
• Stabilization PR

Unresolved questions

None so far.

Implementation history

• Add support for macro expansion in rustdoc source code pages #137229