valtree's to_le() actually produces different result on big-endian from little-endian.

[oli-obk]

   For commit https://github.com/rust-lang/rust/pull/96591/commits/e14b34c386ad2809e937e0e6e0379c5cc5474954 , the two `to_le()` actually produces different result on big-endian from little-endian.

// Note: Don't use `StableHashResult` impl of `u64` here directly, since that
// would lead to endianness problems.
let hash: u128 = hasher.finish();
let hash_short = (hash.to_le() as u64).to_le();

Assume hash: u128=0x5e0f03940fda80bb6348c650c7b26618, then on LE, hash_short: u64 = 0x6348c650c7b26618, while BE hash_short: u64 = 0x5e0f03940fda80bb, which fails some unit tests on big endian targets because of hash mismatch.

If it's expected behavior to make hash value the same on BE/LE, code here should remove two to_le calls. We don't need to adjust endianness unless converting between multi-byte integer and byte sequences.

Originally posted by @ecnelises in #96591 (comment)

[Rageking8]

@rustbot label +C-bug

[ecnelises]

Can we close this now? (I forgot to mention Fixed xxxx in commit msg to trigger the bot) Not sure if I have the permission

@rustbot close

[rustbot]

Error: The feature close is not enabled in this repository.
To enable it add its section in the triagebot.toml in the root of the repository.

Please file an issue on GitHub at triagebot if there's a problem with this bot, or reach out on #t-infra on Zulip.