There are two places that handle normal delayed bugs. This commit
factors out some repeated code.

Also, we can use `std::mem::take` instead of `std::mem::replace`.

Without the starting place, it's hard to retrieve any useful information
from visiting a projection.

…r=pnkfelix"

This reverts commit 503e129, reversing
changes made to 0e7f91b.

…to, r=pnkfelix"

This reverts commit 8c2b577, reversing
changes made to 9cf18e9.

… r=lcnr

Remove special-casing around `AliasKind::Opaque` when structurally resolving in new solver

This fixes a few inconsistencies around where we don't eagerly resolve opaques to their (locally-defined) hidden types in the new solver. It essentially allows this code to work:
```rust
fn main() {
    type Tait = impl Sized;
    struct S {
        i: i32,
    }
    let x: Tait = S { i: 0 };
    println!("{}", x.i);
}
```

Since `Tait` is defined in `main`, we are able to poke through the type of `x` with deref.

r? lcnr

… r=davidtwco

Check rust lints when an unknown lint is detected

Fixes rust-lang#118183

…ed-bugs, r=oli-obk,nnethercote

Give me a way to emit all the delayed bugs as errors (add `-Zeagerly-emit-delayed-bugs`)

This is probably a *better* way to inspect all the delayed bugs in a program that what exists currently (and therefore makes it very easy to choose the right number `N` with `-Zemit-err-as-bug=N`, though I guess the naming is a bit ironic when you pair both of the flags together, but that feels like naming bikeshed more than anything).

This pacifies my only concern with rust-lang#119871 (comment), because (afaict?) that PR doesn't allow you to intercept a delayed bug's stack trace anymore, which as someone who debugs the compiler a lot, is something that I can *promise* that I do.

r? `@nnethercote` or `@oli-obk`

…oli-obk

Add more information to `visit_projection_elem`

Without the starting place, it's hard to retrieve any useful information from visiting a projection.

Note: I still need to add a test.

…avidtwco

Rename `--env` option flag to `--env-set`

As discussed [on zulip](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Stabilizing.20.60--env.60.20option.20flag.3F). We rename `--env` to not conflicting names with the [RFC](rust-lang/rfcs#2794).

r? `@davidtwco`

…enkov

Revert rust-lang#113923

Per [#t-compiler/meetings > [weekly] 2024-01-11](https://rust-lang.zulipchat.com/#narrow/stream/238009-t-compiler.2Fmeetings/topic/.5Bweekly.5D.202024-01-11) discussion, revert rust-lang#113923. Also revert associated rust-lang#118568.

The PR rust-lang#113923 causes the regression issue rust-lang#118609. We need more time to find a proper solution.

Discussions start at [412365838](https://rust-lang.zulipchat.com/#narrow/stream/238009-t-compiler.2Fmeetings/topic/.5Bweekly.5D.202024-01-11/near/412365838) and continue to [412369643](https://rust-lang.zulipchat.com/#narrow/stream/238009-t-compiler.2Fmeetings/topic/.5Bweekly.5D.202024-01-11/near/412369643).

Fixes rust-lang#118609.

r? compiler