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

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

Add a new trait to be generated by diagnostic derives which uses a
`LintDiagnosticBuilder`.

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

Move the logic for building a field mapping (which is used by the
building of format strings in `suggestion` annotations) into a helper
function.

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

`sess` field of `SessionDiagnosticDeriveBuilder` is never actually used
in the builder's member functions, so it doesn't need to be a field.

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

`SessionDiagnostic` isn't suitable for use on lints as whether or not it
creates an error or a warning is decided at compile-time by the macro,
whereas lints decide this at runtime based on the location of the lint
being reported (as it will depend on the user's `allow`/`deny`
attributes, etc). Re-using most of the machinery for
`SessionDiagnostic`, this macro introduces a `LintDiagnostic` derive
which implements a `DecorateLint` trait, taking a
`LintDiagnosticBuilder` and adding to the lint according to the
diagnostic struct.

Mainly intended as a small typo fix ("aliass" -> "aliases") for
the case where a type cannot be found in scope, and there are
multiple inaccessible type aliases that match the missing type.

In general this change would use the correct plural form in
this scenario for words that end with 's'.

Only compute DefKind through the query.

…ve, r=oli-obk

macros: `LintDiagnostic` derive

- Move `LintDiagnosticBuilder` into `rustc_errors` so that a diagnostic derive can refer to it.
- Introduce a `DecorateLint` trait, which is equivalent to `SessionDiagnostic` or `AddToDiagnostic` but for lints. Necessary without making more changes to the lint infrastructure as `DecorateLint` takes a `LintDiagnosticBuilder` and re-uses all of the existing logic for determining what type of diagnostic a lint should be emitted as (e.g. error/warning).
- Various refactorings of the diagnostic derive machinery (extracting `build_field_mapping` helper and moving `sess` field out of the `DiagnosticDeriveBuilder`).
- Introduce a `LintDiagnostic` derive macro that works almost exactly like the `SessionDiagnostic` derive macro  except that it derives a `DecorateLint` implementation instead. A new derive is necessary for this because `SessionDiagnostic` is intended for when the generated code creates the diagnostic. `AddToDiagnostic` could have been used but it would have required more changes to the lint machinery.

~~At time of opening this pull request, ignore all of the commits from rust-lang#98624, it's just the last few commits that are new.~~

r? `@oli-obk`

fix typo in function name

I don't know what I was doing when I named that function...
follow-up to rust-lang#98888
r? `@oli-obk`

…alias_plural_typo, r=lcnr

fix typo in note about multiple inaccessible type aliases

Mainly intended as a small typo fix ("aliass" -> "aliases") for the case where a type cannot be found in scope but there are multiple inaccessible type aliases that match the missing type.

In general this change would use the correct plural form in this scenario for base words that end with 's'.

assert Scalar sanity

With rust-lang#96814 having landed, finally our `Scalar` layouts have the invariants they deserve. :)