Function open_temporary 

pub fn open_temporary(path: &Path, mode: Option<u32>) -> Result<File>

Opens path for writing on the condition that nothing already sits there — a pre-existing file, and a symlink regardless of its target, both fail with AlreadyExists per POSIX O_CREAT|O_EXCL semantics (on wasm32-wasip1, a symlink leaving the sandbox instead fails with ENOTCAPABLE — see [is_planted_symlink_refusal]), so the call never writes through a planted link. A first residue is cleared and the create is retried once; a second refusal — the residue could not be removed, or the path was claimed again in the instant after clearing it — surfaces as an AtomicTemporaryFileError wrapped in the returned io::Error (see AtomicTemporaryFileError::downcast).