this uses some # directives to make sure the code works on x86_64, and does not produce errors on other platforms

Before:

    let a =
        StructWithSomeFields{
            field_1: 1,

            field_2: 2,

            field_3: 3,

            field_4: 4,

            field_5: 5,

            field_6: 6,};

    let a = StructWithSomeFields{ field_1: 1,  field_2: 2, ..a};

After:

    let a =
        StructWithSomeFields {
            field_1: 1,
            field_2: 2,
            field_3: 3,
            field_4: 4,
            field_5: 5,
            field_6: 6 };

    let a = StructWithSomeFields { field_1: 1, field_2: 2, ..a };

…one, r=onur-ozkan

bootstrap: Avoid cloning `change-id` list

Inspired by [recent discussion](https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/Collecting.20some.20Real.20Configs.20for.20testing/near/507845657) on the bootstrap `change-id` field, I took a look at the code and found this little optimization. It does not change behavior.

…errors

Properly document FakeReads

…-check-block, r=GuillaumeGomez

unstable book: in a sanitizer example, check the code

Use some `#` directives to make sure the code checks on x86_64, and does not produce errors on other platforms. This example still used an older version of `#[naked]`, and because the snippet was ignored that was missed before.

I'm not sure when this gets built on CI exactly, so it might be worthwhile to try and build it for a non-x86_64 architecture to make sure that works. I'm not sure how to verify locally that e.g. on aarch64 this code works without errors/warnings.

…rors

Remove attribute `#[rustc_error]`

It was an ancient way to write `check-pass` tests, but now it's no longer necessary (except for the `delayed_bug_from_inside_query` flavor, which is retained).

…iler-errors

Improve hir_pretty for struct expressions.

While working on rust-lang#139131 I noticed the hir pretty printer outputs an empty line between each field, and is also missing a space before the `{` and the `}`:

```rust
    let a =
        StructWithSomeFields{
            field_1: 1,

            field_2: 2,

            field_3: 3,

            field_4: 4,

            field_5: 5,

            field_6: 6,};

    let a = StructWithSomeFields{ field_1: 1,  field_2: 2, ..a};
```

This changes it to:

```rust
    let a =
        StructWithSomeFields {
            field_1: 1,
            field_2: 2,
            field_3: 3,
            field_4: 4,
            field_5: 5,
            field_6: 6 };

    let a = StructWithSomeFields { field_1: 1, field_2: 2, ..a };
```

Switch some rustc_on_unimplemented uses to diagnostic::on_unimplemented

The use on the SliceIndex impl appears unreachable, there is no mention of "vector indices" in any test output and I could not get it to show up in error messages.