Improve error message when incorrectly using the || operator instead of or

[MaddyGuthridge]

Zig Version

0.13.0

Steps to Reproduce and Observed Output

In the following code, I incorrectly used || instead of or (likely a common beginner mistake).

fn example(x: i32, y: i32) bool {
    return
        x < y
        || x > y + 10
        || y - x == 5;
}

The compiler gives an error about chaining comparison operators, likely because || has a higher precedence than comparison operators.

main.zig:12:24: error: comparison operators cannot be chained
            || pos.col < 0
                       ^

Expected Output

Instead, it would be much more helpful to give an error suggesting the or keyword instead of the || operator. This could be detected by using the fact that || is not defined for anything except for the Error Set Type, meaning that even without the comparison operators, it would not be allowed to compile.

[nektro]

related: #15526