New lint: Manual assert

[camsteffen]

What it does

Detects if-then-panic! that can be replaced with assert!

Categories (optional)

• Kind: style

What is the advantage of the recommended code over the original code

It is simpler

Drawbacks

None.

Example

if !sad_people.is_empty() {
    panic!("there are sad people: {:?}", sad_people);
}

Could be written as:

assert!(sad_people.is_empty(), "there are sad people: {:?}", sad_people);

Lint name: manual_assert or if_then_panic

[matthiaskrgr]

What about its with multiple conditions?
If we have 10-5 conditions it does probably not help a lot, to use a super big assert...

[camsteffen]

We could lint only if the condition expression currently fits on one line.

[Labelray]

@rustbot claim