Understanding Rust Error E0030: Non-Empty Range Patterns
Rust Error E0030 Explanation
Rust Error E0030 occurs when you use a range pattern that is empty. In Rust, range patterns are used for value matching and consist of a start and an end value, both of which are inclusive. The error is triggered when the range's start value is greater than its end value, which would result in an empty range.
Example of Error E0030
Consider the following code example, where we trigger Rust Error E0030 by using an empty range pattern:
```rust
#![allow(unused)]
fn main() {
match 5u32 {
1 ..= 1 => {},
1000 ..= 5 => {}
}
}
```Here, we have an empty range pattern (1000 ..= 5), which results in a compile-time error, as the start value (1000) is greater than the end value (5).
Fixing Rust Error E0030
To fix Rust Error E0030, ensure that your range pattern is non-empty. This means that the start value of the range must be less than or equal to the end value. Modify the erroneous code:
```rust
#![allow(unused)]
fn main() {
match 5u32 {
1 ..= 1 => {},
1 ..= 5 => {}
}
}
```In this corrected code, the range pattern (1 ..= 5) is non-empty, as the start value (1) is less than or equal to the end value (5).
Conclusion
Rust Error E0030 is related to empty range patterns in match expressions. To resolve this error, verify that your range patterns are non-empty by ensuring that the start value is less than or equal to the end value. By doing so, you'll create a valid, non-empty range pattern that can be used in your Rust code.