E0421: Unknown enum type

Explanation

An enum variant pattern names an enum type that cannot be resolved in that pattern's scope. This diagnostic is specific to enum-pattern lookup; an unresolved bare name in a value expression follows ordinary undefined-name diagnostics instead.

Likely cause

The pattern's enum name is misspelled, is not visible in the current module, or names a different kind of item. Use an enum type available in the pattern's scope and spell its path correctly.

Examples

Unknown enum type in a pattern

enum Color { Red, Blue }
fn main() -> i32 {
    let color = Color.Red;
    match color {
        Shade.Red => 1,
        _ => 0,
    }
}

Use the resolved enum type

enum Color { Red, Blue }
fn main() -> i32 {
    let color = Color.Red;
    match color {
        Color.Red => 1,
        Color.Blue => 0,
    }
}

References

• Enum variant pattern syntax

• Enum variant name lookup