Allow currency groupings in inconsistent_digit_grouping

I'm writing a program which stores some amount of cents as an unsigned integer. It's basically a fixed-point decimal. So, it makes sense to place an underscore before the last two digits, but clippy flips out over this. For example, the following does not pass the lint:

fn one_million_dollars() -> u64 {
    1_000_000_00
}

I propose that the behavior should be changed so that literals with no fractional part can have a final grouping of two digits. If everyone agrees, I'd be willing to implement the change myself.

[flip1995]

I think this is really specific to your use case. For such specific cases, where a lint doesn't make sense, because of some semantics that cannot be statically checked, #[allow(..)] exists.

You could also write this as

fn one_million_dollars() -> u64 {
    1_000_000 * 100
}

which would make the intention clearer IMO, without losing performance since the expression gets const evaluated anyway.

To represent other values than 00 for cents, you could use 1_000_000 * 100 + 42, which again gets const evaluated.

Do you have other use cases in mind, where xxx_yz would make sense?

No.