Port the "unconstrained opaque type" diagnostic to using the diagnostic
derive.

Signed-off-by: David Wood <david.wood@huawei.com>

Diagnostics can have multiple primary spans, or have subdiagnostics
repeated at multiple locations, so support `Vec<..>` fields in the
diagnostic derive which become loops in the generated code.

Signed-off-by: David Wood <david.wood@huawei.com>

Currently, the only API for creating errors from a diagnostic derive
will emit it immediately. This makes it difficult to add subdiagnostics
to diagnostics from the derive, so add `create_{err,warning}` functions
that return the diagnostic without emitting it.

Signed-off-by: David Wood <david.wood@huawei.com>

Port the "explicit generic arguments with impl trait" diagnostic to
using the diagnostic derive.

Signed-off-by: David Wood <david.wood@huawei.com>

make Size and Align debug-printing a bit more compact

In particular in `{:#?}`-mode, these take up a lot of space, so I think this is the better alternative (even though it is a bit longer in `{:?}` mode, I think it is still more readable).

We could make it even smaller by deviating further from what the actual code looks like, e.g. via something like `Size(4 bytes)`. Not sure what people would think about that?

Cc `````@oli-obk`````

…ession, r=notriddle

Fix jump to def regression

rust-lang#93803 introduced a regression in the "jump to def" feature. This fixes it.

Nice side-effect: it adds a new regression test. :)

I also used this opportunity to add documentation about this unstable feature in the rustdoc book.

cc ``@cjgillot``
r? ``@notriddle``

…c, r=oli-obk

diagnostics: port more diagnostics to derive + add support for `Vec` fields

- Port "unconstrained opaque type" diagnostic to using the derive.
- Allow `Vec` fields in diagnostic derive - enables support for diagnostics that have multiple primary spans, or have subdiagnostics repeated at multiple locations. `Vec<..>` fields in the diagnostic derive become loops in the generated code.
- Add `create_{err,warning}` - there wasn't a way to create a diagnostic from a struct and not emit it straight away.
- Port "explicit generic args w/ impl trait" diagnostic to using the derive.

r? `````@oli-obk`````
cc `````@pvdrz`````

Improve validator around field projections and checked bin ops

The two commits are unrelated. In both cases, these rules were already documented in MIR docs.

Change eslint rules from configuration comments to configuration file

Repeatedly declaring eslint rules in source files is an annoying thing, we should move those rules into the eslint configuration file.

r? ``@GuillaumeGomez``

update Miri

Fixes rust-lang#96773
r? ``@ghost``

…ix, r=JohnTitor

Fix a minor typo in the description of Formatter