Rust errors / Types and traits
Rust compiler error · checked with rustc 1.99.0
Rust error E0030: lower bound for range pattern must be less than or equal to upper bound
What it meansWhen matching against a range, the compiler verifies that the range is non-empty. Range patterns include both end-points, so this is equivalent to requiring the start of the range to be less than or equal to the end of the range.
What rustc prints
error[E0030]: lower bound for range pattern must be less than or equal to upper bound
--> main.rs:7:5
|
7 | 1000 ..= 5 => {}
| ^^^^^^^^^^ lower bound larger than upper boundReal output of rustc 1.99.0 compiling the official example below (2021 edition). Your names and line numbers will differ; the first line is the part to match.
The compiler team's explanation
When matching against a range, the compiler verifies that the range is non-empty. Range patterns include both end-points, so this is equivalent to requiring the start of the range to be less than or equal to the end of the range.
Erroneous code example:
match 5u32 {
// This range is ok, albeit pointless.
1 ..= 1 => {}
// This range is empty, and the compiler can tell.
1000 ..= 5 => {}
}From rustc --explain E0030 (1.99.0), part of the Rust project, MIT or Apache-2.0. Official page.
Related errors
- E0308mismatched types
- E0277the trait bound is not satisfied
- E0599no method named X found in the current scope
- E0433failed to resolve
- E0025field `a` bound multiple times in the pattern
- E0029only `char` and numeric types are allowed in range patterns
- E0033A trait type has been dereferenced
- E0038For any given trait `Trait` there may be a related _type_ called the _trait object type_ which is typically written as `dyn Trait`. In earlier editions of Rust, trait object types were written as plain `Trait` (just the name of the trait, written in type positions) but this was a bit too confusing, so we now write `dyn Trait`
Up next
Often hit nextE0308: mismatched typesA related error from the same family.Read it next →Did this answer your question?