Namely closures and `async` blocks. We have to make a few modifications
to closures to make them compile.

… return types

This helper method works for all types, falling back to a query for
`TyKind::Adt`s to determine whether the implement the
`{Partial,}StructuralEq` traits.

…atthewjasper

On recursive ADT, provide indirection structured suggestion

…, r=nikomatsakis

Further tweak lifetime errors involving `dyn Trait` and `impl Trait` in return position

* Suggest substituting `'static` lifetime in impl/dyn `Trait + 'static` instead of `Trait + 'static + '_`
* When `'static` is explicit, also suggest constraining argument with it
* Reduce verbosity of suggestion message and mention lifetime in label
* Tweak output for overlapping required/captured spans
* Give these errors an error code

Follow up to rust-lang#72543.

r? @nikomatsakis

…, r=pnkfelix

Querify whether a type has structural equality (Take 2)

Alternative to rust-lang#72177.

Unlike in rust-lang#72177, this helper method works for all types, falling back to a query for `TyKind::Adt`s that determines whether the `{Partial,}StructuralEq` traits are implemented.

This is my preferred interface for this method. I think this is better than just documenting that the helper only works for ADTs. If others disagree, we can just merge rust-lang#72177 with the fixes applied. This has already taken far too long.

…op, r=pnkfelix

Preserve `Expr`s that have `DefId`s in `ReplaceBodyWithLoop`

This PR fixes the last part of rust-lang#71104 by preserving expressions that are assigned their own `DefId`s (closures and `async` blocks) when passing them to `rustdoc`. This avoids having a `DefId` without a corresponding `HirId`.

The first commit in this PR makes `-Zunpretty=everybody_loops` actually work again, and the subsequent two are miscellaneous cleanup. They should probably get merged regardless of what we end up doing here.

Sample input:
```rust
fn foo() -> Box<i32> {
    let x = |a: i64| {
        const FOO: i64 = 1;
    };

    let a = 4;
    Box::new(a)
}
```

Sample output:
```rust
fn foo() -> Box<i32> {
    || -> !
        {
            const FOO: i64 = 1;
            loop  { }
        };
    loop  { }
}
```

r? @ghost

…Simulacrum

Use the built cargo for cargotest.

cargotest was using the beta (bootstrap) cargo. This changes it so that it will use the locally built cargo. This is intended to provide a sort of smoke test to ensure Cargo is functional. This *shouldn't* have any real impact on the CI build time.  The cargotest job also happens to run cargo's testsuite, so it should already be building cargo.

Note: This will fail until rust-lang#73266 is merged.

…i-obk

fix caller_location intrinsic for Miri

Fixes rust-lang#73272

r? @oli-obk Cc @Aaron1011