Suggested lint for numeric literals with leading unary negation

[PhilipDaniels]

I recently posted a thread on Rust Users when I was tripped up by this piece of code

if a >- 150 {

It's a simple typo (it should be >=), but quite difficult to spot. It's not currently warned on by clippy.
A user on the thread did point out that the current behaviour is similar to what happens in other languages, and is not in fact ambiguous with respect to precedence, however, I wondered if people think it worth a lint? It took me an hour or so to find this error.

I can think of two 'problems' with the above that could be converted to a lint:

• The - should not be separated from the literal
• >- is not a valid operator.

Of the two, the first is probably a better candidate, as I know there is a tendency for some programmmers to eschew whitespace when writing mathematial expressions making things such as if a>-150 { or x*x>90 quite common (perhaps more so in C than in Rust).

The title says unary negation, but I guess + 200 ought to be considered as well.

[flip1995]

We could add a (pedantic) lint for the first case you described.

But as already pointed out in the forum thread, rustfmt automatically formats this to if a > -150 { (Playground example). Since many people run rustfmt on save, this lint would not trigger or them and I don't really see another way to detect this.

This is similar to suspicious_assignment_formatting. IMO, it would make sense to call it 'suspicious_comparison_formatting' and put it in the style group.

Or maybe this check can be applied to all binary operations. 🤔

[nikofil]

Hey! I made a PR about this issue to get my feet wet with this project. I hope I understood @mikerite's suggestion about doing this check on all binary operations correctly - this way makes sense to me. All feedback welcome!