…available

Windows 10 1601 introduced `FileRenameInfoEx` as well as
`FILE_RENAME_FLAG_POSIX_SEMANTICS`, allowing for atomic renaming. If it
isn't supported, we fall back to `FileRenameInfo`.

This commit also replicates `MoveFileExW`'s behavior of checking whether
the source file is a mount point and moving the mount point instead of
resolving the target path.

… opened and for renaming over a non-empty directory

This updates the Fuchsia SDK used to test rust on Fuchsia to
26.20241211.7.1, and clang to the development version 20 from
388d7f144880dcd85ff31f06793304405a9f44b6.

It seems that cargo can't conditionally propagate features
when `default-features` is set to `false`.

Signed-off-by: onur-ozkan <work@onurozkan.dev>

The "panic in const if CTFE doesn't know the answer" behavior was discussed to be the desired behavior in rust-lang#74939, and is currently how the function actually behaves.

I intentionally wrote this documentation to allow for the possibility that a panic might not occur even if the pointer is out of bounds, because of rust-lang#133700 and other potential changes in the future.

…antics, r=ChrisDenton

Win: Use POSIX rename semantics for `std::fs::rename` if available

Windows 10 1601 introduced `FileRenameInfoEx` as well as `FILE_RENAME_FLAG_POSIX_SEMANTICS`, allowing for atomic renaming and renaming if the target file is has already been opened with `FILE_SHARE_DELETE`, in which case the file gets renamed on disk while the open file handle still refers to the old file, just like in POSIX. This resolves rust-lang#123985, where atomic renaming proved difficult to impossible due to race conditions.

If `FileRenameInfoEx` isn't available due to missing support from the underlying filesystem or missing OS support, the renaming is retried with `FileRenameInfo`, which matches the behavior of `MoveFileEx`.

This PR also manually replicates parts of `MoveFileEx`'s internal logic, as reverse-engineered from the disassembly: If the source file is a reparse point and said reparse point is a mount point, the mount point itself gets renamed; otherwise the reparse point is resolved and the result renamed.

Notes:
- Currently, the `win7` target doesn't bother with `FileRenameInfoEx` at all; it's probably desirable to remove that special casing and try `FileRenameInfoEx` anyway if it doesn't exist, in case the binary is run on newer OS versions.

Fixes rust-lang#123985

Correctly document CTFE behavior of is_null and methods that call is_null.

The "panic in const if CTFE doesn't know the answer" behavior was discussed to be the desired behavior in rust-lang#74939, and is currently how the function actually behaves.

I intentionally wrote this documentation to allow for the possibility that a panic might not occur even if the pointer is out of bounds, because of rust-lang#133700 and other potential changes in the future.

This is beta-nominated since `const fn is_null` stabilization is in beta already but the docs there are wrong, and it seems better to have the docs be correct at the time of stabilization.

…ieyouxu

update `rustc_index_macros` feature handling

It seems that cargo can't [conditionally propagate features](https://github.com/rust-lang/rust/blob/214587c89d527dd0ccbe1f2150c737d3bdee67b0/compiler/rustc_index/Cargo.toml#L20) if they were enabled by default on the target crate, but disabled with `default-features = false` in the current/parent crate.

Fixes rust-lang#118129

Bump Fuchsia toolchain for testing

This updates the Fuchsia SDK used to test rust on Fuchsia to 26.20241211.7.1, and clang to the development version 20 from 388d7f144880dcd85ff31f06793304405a9f44b6.

```@steven807``` asked me to take over the PR. Since I don't have commit access to his repo, I just cherry picked his patch here.

try-job: dist-various-2

r? lqd

on pair → on par