Ruta graveolens  ·  notes from a language experiment  ·  cultivated since 2025

E0006: Uppercase base prefix

CodeCategoryStability
E0006LexerPermanent

Explanation

An integer literal uses an uppercase base prefix. Rue requires the prefix itself to be lowercase, although hexadecimal digits after 0x may be uppercase.

Likely cause

The literal begins with 0X, 0O, or 0B, perhaps copied from a language that accepts uppercase prefixes. Write 0x, 0o, or 0b instead.

Examples

Uppercase hexadecimal prefix

fn main() {
    let value = 0XFF;
}

Lowercase prefix with uppercase digits

fn main() -> i32 {
    0xFF
}

References