Disable cast_lossless when casting to u128 from any (u)int type

[Jacherr]

Fixes #12492

Disables cast_lossless when casting to u128 from any int or uint type. The lint states that when casting to any int type, there can potentially be lossy behaviour if the source type ever exceeds the size of the destination type in the future, which is impossible with a destination of u128.

It's possible this is a bit of a niche edge case which is better addressed by just disabling the lint in code, but I personally couldn't think of any good reason to still lint in this specific case - maybe except if the source is a bool, for readability reasons :).

changelog: FP: cast_lossless: disable lint when casting to u128 from any (u)int type

[rustbot]

r? @blyxyas

rustbot has assigned @blyxyas.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[Alexendoo]

I think the lint still applies here, the message could be updated but replacing a lossless cast with from is still a good suggestion

The type of the RHS could be changed in the future for example to a lossy cast

[blyxyas]

Meow meow meow =^w^=

[blyxyas]

Casting from a u128 to a i128 could be dangerous. u128 is the only data type that we can be sure that they won't cause an error.

Suggested change

	&& (matches!(cast_to.kind(), ty::Int(IntTy::I128)) || matches!(cast_to.kind(), ty::Uint(UintTy::U128))))
	&& matches!(cast_to.kind(), ty::Uint(UintTy::U128))

[blyxyas]

Sorry for the delay, I actually viewed this change the day you committed it but forgot to approve it 😅

LGTM, thanks! ❤️ Could you squash the commits into one?

[blyxyas]

@bors r+

[bors]

📌 Commit 477108d has been approved by blyxyas

It is now in the queue for this repository.

[bors]

⌛ Testing commit 477108d with merge 34766a6...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: blyxyas
Pushing 34766a6 to master...