Use binary radix in `bitflags!`

[Centri3]

What it does

Checks for use of hexadecimal (0x), decimal, octal (0o), etc in a bitflags! invocation, suggesting 0b instead.

Advantage

• It's a bitflags type, so using binary is easier to understand as it doesn't require mental math to convert between the two (e.g., what bit is set for 0x1000?).

Drawbacks

• Can be worse in cases where it matches external constants, like for example: https://learn.microsoft.com/en-us/windows/win32/Memory/memory-protection-constants, winapi documentation tends to use hexadecimal instead, so I'd expect a Protection bitflags to use it too. So it should be restriction or pedantic.

Example

bitflags! {
	#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
	struct Flags: u32 {
		const A = 0x1000;
	}
}

Could be written as:

bitflags! {
	#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
	struct Flags: u32 {
		const A = 0b1000000000000;
	}
}

[Centri3]

We tend not to add lints for external crates but I think bitflags is common enough to warrant it :)