Check if if conditions always evaluate to true in never_loop

[Centri3]

This fixes the example provided in #11004, but it shouldn't be closed as this is still an issue on like

let x = true;
if x { /* etc */ }`

This also makes clippy_utils::consts::constant handle ConstBlock and DropTemps.

changelog: [never_loop]: Check if if conditions always evaluate to true

[rustbot]

r? @giraffate

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[blyxyas]

I'm amazed with the complexity of this lint, I feel like it could be so much simpler 😅.
Just checking if there's something before a return / break should be enough, right? Maybe I'm missing something important here.

[Centri3]

I suppose so, but then there's something like

if false {
	break 'a;
}
return;

You're basically switching a few FPs for a whole bunch of FNs, pick your poison I suppose. I think the current way is fine and only has its shortcomings here, with unevaluable conditions

[giraffate]

@bors r+

Thanks!

[bors]

📌 Commit 6a1084c has been approved by giraffate

It is now in the queue for this repository.

[bors]

⌛ Testing commit 6a1084c with merge 407bfd4...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: giraffate
Pushing 407bfd4 to master...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: giraffate
Pushing 407bfd4 to master...