Per discussion in #84326. For trait implementations, this was
misleading: the items actually do have documentation (but it comes from
the trait definition).
For both trait implementations and trait implementors, this was
redundant: in both of those cases, the items are default-hidden by
different toggle at the level above.
Update tests: Remove XPath selectors that over-specified on details tag,
in cases that weren't testing toggles. Add an explicit test for toggles
on methods. Rename item-hide-threshold to toggle-item-contents for
consistency.
This sets their toggles to be closed in the HTML (matching the default
setting), and opens them if the setting indicates to do so.
This distinguishes between implementations and implementors based on
being descendants of certain named elements.
We don't want to render default item docs but previously
`doctraititem` naively delegated to the trait definition in those
cases.
Updated tests to also check that this doesn't strip default item
docs from the trait definition.
In `test/rustdoc/manual_impl.rs` there are now three structs:
* S1 implements and documents required method `a_method`.
* S2 implements and documents `a_method` as well as provided
method `b_method`.
* S3 implements `a_method` and `b_method`, but only documents
`b_method`.
For a struct, we want the rendered trait impls to include documentation
if and only if it appears on the trait implementation itself
(since users can just go to the trait definition for anything not
covered in the impl docs). This means we expect:
* S1, S2, and S3 to all include top-level trait impl docs.
* S1, S2, and S3 to exclude all trait definition docs.
* S1 to show impl docs for `a_method`.
* S2 to show impl docs for `a_method` and `b_method`.
* S3 to show impl docs for `b_method`.
These tests cover those cases.
