That is, change `diagnostic_outside_of_impl` and
`untranslatable_diagnostic` from `allow` to `deny`, because more than
half of the compiler has be converted to use translated diagnostics.

This commit removes more `deny` attributes than it adds `allow`
attributes, which proves that this change is warranted.

This rewrite makes the cache-updating nature of the function slightly clearer, using the Entry API into the hash table for region names to capture the update-insert nature of the method. May be marginally more efficient since it only runtime-borrows the map once, but in this context the performance impact is almost certainly completely negligible.

…visit

This prevents ICEs from happening in the future when this code path is actually used

…ariants

When you stash an error, the error count is incremented. You can then
use the non-zero error count to get an `ErrorGuaranteed`. You can then
steal the error, which decrements the error count. You can then cancel
the error.

Example code:
```
fn unsound(dcx: &DiagCtxt) -> ErrorGuaranteed {
    let sp = rustc_span::DUMMY_SP;
    let k = rustc_errors::StashKey::Cycle;
    dcx.struct_err("bogus").stash(sp, k);           // increment error count on stash
    let guar = dcx.has_errors().unwrap();           // ErrorGuaranteed from error count > 0
    let err = dcx.steal_diagnostic(sp, k).unwrap(); // decrement error count on steal
    err.cancel();                                   // cancel error
    guar                                            // ErrorGuaranteed with no error emitted!
}
```

This commit fixes the problem in the simplest way: by not counting
stashed errors in `DiagCtxt::{err_count,has_errors}`.

However, just doing this without any other changes leads to over 40 ui
test failures. Mostly because of uninteresting extra errors (many saying
"type annotations needed" when type inference fails), and in a few
cases, due to delayed bugs causing ICEs when no normal errors are
printed.

To fix these, this commit adds `DiagCtxt::stashed_err_count`, and uses
it in three places alongside `DiagCtxt::{has_errors,err_count}`. It's
dodgy to rely on it, because unlike `DiagCtxt::err_count` it can go up
and down. But it's needed to preserve existing behaviour, and at least
the three places that need it are now obvious.

When launching tests with --keep-stage option, startup objects
such as rsbegin.o an rsend.o may disappear from the corresponding
stageN compiler.

Fix issue rust-lang#120784

…ochenkov

Make privacy visitor use types more (instead of HIR)

r? ``@petrochenkov``

This is a prerequisite to normalizing projections, as otherwise we have too many invalid bound vars (hir_ty_to_ty is creating types that have bound vars, but no binder).

The commits are still chaotic, I'm gonna clean them up, but I just wanted to let you know about the general direction and wondering if we could land this before adding normalization, as normalization is where behavioral changes happen, and I'd like to keep that part as minimal as possible.

[context can be found on zulip](https://rust-lang.zulipchat.com/#narrow/stream/315482-t-compiler.2Fetc.2Fopaque-types/topic/weak.20type.20aliases.20and.20privacy)

…ou-se

core/time: avoid divisions in Duration::new

In our (decently large) code base, we use `SystemTime::UNIX_EPOCH.elapsed()` in a lot of places & often in a loop or in the hot path. On [Unix](https://github.com/rust-lang/rust/blob/1.75.0/library/std/src/sys/unix/time.rs#L153-L162) at least, it seems we do calculations before hand to ensure that nanos is within the valid range, yet `Duration::new()` still checks it again, using 2 divisions. It seems like adding a branch can make this function 33% faster on ARM64 in the cases where nanos is already in the valid range & seems to have no effect in the other case.

Benchmarks:
M1 Pro (14-inch base model):
```
duration/current/checked
                        time:   [1.5945 ns 1.6167 ns 1.6407 ns]
Found 5 outliers among 100 measurements (5.00%)
  2 (2.00%) high mild
  3 (3.00%) high severe
duration/current/unchecked
                        time:   [1.5941 ns 1.6051 ns 1.6179 ns]
Found 2 outliers among 100 measurements (2.00%)
  1 (1.00%) high mild
  1 (1.00%) high severe

duration/branched/checked
                        time:   [1.1997 ns 1.2048 ns 1.2104 ns]
Found 8 outliers among 100 measurements (8.00%)
  4 (4.00%) high mild
  4 (4.00%) high severe
duration/branched/unchecked
                        time:   [1.5881 ns 1.5957 ns 1.6039 ns]
Found 6 outliers among 100 measurements (6.00%)
  3 (3.00%) high mild
  3 (3.00%) high severe
```
EC2 c7gd.16xlarge (Graviton 3):
```
duration/current/checked
                        time:   [2.7996 ns 2.8000 ns 2.8003 ns]
Found 5 outliers among 100 measurements (5.00%)
  2 (2.00%) low severe
  3 (3.00%) low mild
duration/current/unchecked
                        time:   [2.9922 ns 2.9925 ns 2.9928 ns]
Found 7 outliers among 100 measurements (7.00%)
  4 (4.00%) low severe
  1 (1.00%) low mild
  2 (2.00%) high mild

duration/branched/checked
                        time:   [2.0830 ns 2.0843 ns 2.0857 ns]
Found 3 outliers among 100 measurements (3.00%)
  1 (1.00%) low severe
  1 (1.00%) low mild
  1 (1.00%) high mild
duration/branched/unchecked
                        time:   [2.9879 ns 2.9886 ns 2.9893 ns]
Found 5 outliers among 100 measurements (5.00%)
  3 (3.00%) low severe
  2 (2.00%) low mild
```
EC2 r7iz.16xlarge (Intel Xeon Scalable-based (Sapphire Rapids)):
```
duration/current/checked
                        time:   [980.60 ps 980.79 ps 980.99 ps]
Found 10 outliers among 100 measurements (10.00%)
  4 (4.00%) low severe
  2 (2.00%) low mild
  3 (3.00%) high mild
  1 (1.00%) high severe
duration/current/unchecked
                        time:   [979.53 ps 979.74 ps 979.96 ps]
Found 6 outliers among 100 measurements (6.00%)
  2 (2.00%) low severe
  1 (1.00%) low mild
  2 (2.00%) high mild
  1 (1.00%) high severe

duration/branched/checked
                        time:   [938.72 ps 938.96 ps 939.22 ps]
Found 4 outliers among 100 measurements (4.00%)
  1 (1.00%) low mild
  1 (1.00%) high mild
  2 (2.00%) high severe
duration/branched/unchecked
                        time:   [1.0103 ns 1.0110 ns 1.0118 ns]
Found 10 outliers among 100 measurements (10.00%)
  2 (2.00%) low mild
  7 (7.00%) high mild
  1 (1.00%) high severe
```

Bench code (ran using stable 1.75.0 & criterion latest 0.5.1):
I couldn't find any benches for `Duration` in this repo, so I just copied the relevant types & recreated it.
```rust
use criterion::{black_box, criterion_group, criterion_main, Criterion};

pub fn duration_bench(c: &mut Criterion) {
    const NANOS_PER_SEC: u32 = 1_000_000_000;

    #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
    #[repr(transparent)]
    struct Nanoseconds(u32);

    impl Default for Nanoseconds {
        #[inline]
        fn default() -> Self {
            // SAFETY: 0 is within the valid range
            unsafe { Nanoseconds(0) }
        }
    }

    #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
    pub struct Duration {
        secs: u64,
        nanos: Nanoseconds, // Always 0 <= nanos < NANOS_PER_SEC
    }

    impl Duration {
        #[inline]
        pub const fn new_current(secs: u64, nanos: u32) -> Duration {
            let secs = match secs.checked_add((nanos / NANOS_PER_SEC) as u64) {
                Some(secs) => secs,
                None => panic!("overflow in Duration::new"),
            };
            let nanos = nanos % NANOS_PER_SEC;
            // SAFETY: nanos % NANOS_PER_SEC < NANOS_PER_SEC, therefore nanos is within the valid range
            Duration { secs, nanos: unsafe { Nanoseconds(nanos) } }
        }

        #[inline]
        pub const fn new_branched(secs: u64, nanos: u32) -> Duration {
            if nanos < NANOS_PER_SEC {
                // SAFETY: nanos < NANOS_PER_SEC, therefore nanos is within the valid range
                Duration { secs, nanos: unsafe { Nanoseconds(nanos) } }
            } else {
                let secs = match secs.checked_add((nanos / NANOS_PER_SEC) as u64) {
                    Some(secs) => secs,
                    None => panic!("overflow in Duration::new"),
                };
                let nanos = nanos % NANOS_PER_SEC;
                // SAFETY: nanos % NANOS_PER_SEC < NANOS_PER_SEC, therefore nanos is within the valid range
                Duration { secs, nanos: unsafe { Nanoseconds(nanos) } }
            }
        }
    }

    let mut group = c.benchmark_group("duration/current");
    group.bench_function("checked", |b| {
        b.iter(|| black_box(Duration::new_current(black_box(1_000_000_000), black_box(1_000_000))));
    });
    group.bench_function("unchecked", |b| {
        b.iter(|| {
            black_box(Duration::new_current(black_box(1_000_000_000), black_box(2_000_000_000)))
        });
    });
    drop(group);
    let mut group = c.benchmark_group("duration/branched");
    group.bench_function("checked", |b| {
        b.iter(|| {
            black_box(Duration::new_branched(black_box(1_000_000_000), black_box(1_000_000)))
        });
    });
    group.bench_function("unchecked", |b| {
        b.iter(|| {
            black_box(Duration::new_branched(black_box(1_000_000_000), black_box(2_000_000_000)))
        });
    });
}

criterion_group!(duration_benches, duration_bench);
criterion_main!(duration_benches);
```

…s, r=davidtwco

Invert diagnostic lints.

That is, change `diagnostic_outside_of_impl` and `untranslatable_diagnostic` from `allow` to `deny`, because more than half of the compiler has been converted to use translated diagnostics.

This commit removes more `deny` attributes than it adds `allow` attributes, which proves that this change is warranted.

r? ````@davidtwco````

…write, r=compiler-errors

A drive-by rewrite of `give_region_a_name()`

This drive-by rewrite makes the cache-updating nature of the method clearer, using the Entry API into the hash table for region names to capture the update-insert nature of the method. May be marginally more efficient since it only runtime-borrows and indexes the map once, but in this context the performance impact is almost certainly completely negligible.

Note that this commit should preserve all externally visible behaviour. Notably, it preserves the debug logging:

1. printing even in the case of a `None` for the new computed name, and
2. only printing on new values, begin silent on reused values

…ructors, r=Nilstrieb

Use `transmute_unchecked` in `NonZero::new`.

Tracking issue: rust-lang#120257

See rust-lang#120521 (comment).

…=oli-obk

Fix more `ty::Error` ICEs in MIR passes

Fixes rust-lang#120791 - Add a check for `ty::Error` in the `ByMove` coroutine pass
Fixes rust-lang#120816 - Add a check for `ty::Error` in the MIR validator

Also a drive-by fix for a FIXME I had asked oli to add

r? oli-obk

…-obk

Fix `ErrorGuaranteed` unsoundness with stash/steal.

When you stash an error, the error count is incremented. You can then use the non-zero error count to get an `ErrorGuaranteed`. You can then steal the error, which decrements the error count. You can then cancel the error.

Example code:
```
fn unsound(dcx: &DiagCtxt) -> ErrorGuaranteed {
    let sp = rustc_span::DUMMY_SP;
    let k = rustc_errors::StashKey::Cycle;
    dcx.struct_err("bogus").stash(sp, k);           // increment error count on stash
    let guar = dcx.has_errors().unwrap();           // ErrorGuaranteed from error count > 0
    let err = dcx.steal_diagnostic(sp, k).unwrap(); // decrement error count on steal
    err.cancel();                                   // cancel error
    guar                                            // ErrorGuaranteed with no error emitted!
}
```

This commit fixes the problem in the simplest way: by not counting stashed errors in `DiagCtxt::{err_count,has_errors}`.

However, just doing this without any other changes leads to over 40 ui test failures. Mostly because of uninteresting extra errors (many saying "type annotations needed" when type inference fails), and in a few cases, due to delayed bugs causing ICEs when no normal errors are printed.

To fix these, this commit adds `DiagCtxt::stashed_err_count`, and uses it in three places alongside `DiagCtxt::{has_errors,err_count}`. It's dodgy to rely on it, because unlike `DiagCtxt::err_count` it can go up and down. But it's needed to preserve existing behaviour, and at least the three places that need it are now obvious.

r? oli-obk

…objects, r=onur-ozkan

Startup objects disappearing from sysroot

When launching tests with --keep-stage option, startup objects such as rsbegin.o an rsend.o may disappear from the corresponding stageN compiler.

Fix issue rust-lang#120784