What causes "cannot apply alias for AsEnum with asterisk" in SeaQL/sea-orm?

Name the concrete column inside the AsEnum expression instead of an asterisk

cannot apply alias for AsEnum with asterisk

Error message

cannot apply alias for AsEnum with asterisk

What it means

When a selected expression is wrapped in SimpleExpr::AsEnum (cast of a column to an enum type), apply_alias inspects the inner expression expecting a concrete Column. If the inner column is an asterisk/wildcard, no column name exists to build the alias from and the library panics with this message.

Source

Thrown at src/query/combine.rs:65

        self.query().exprs_mut_for_each(|sel| {
            match &sel.alias {
                Some(alias) => {
                    let alias = format!("{}{}", pre, alias.to_string().as_str());
                    sel.alias = Some(alias.into_iden());
                }
                None => {
                    let col = match &sel.expr {
                        SimpleExpr::Column(col_ref) => match col_ref.column() {
                            Some(col) => col,
                            None => {
                                panic!("cannot apply alias for Column with asterisk");
                            }
                        },
                        SimpleExpr::AsEnum(_, simple_expr) => match simple_expr.as_ref() {
                            SimpleExpr::Column(col_ref) => match col_ref.column() {
                                Some(col) => col,
                                None => {
                                    panic!("cannot apply alias for AsEnum with asterisk")
                                }
                            },
                            _ => {
                                panic!("cannot apply alias for AsEnum with expr other than Column")
                            }
                        },
                        _ => panic!("cannot apply alias for expr other than Column or AsEnum"),
                    };
                    let alias = format!("{}{}", pre, col.to_string().as_str());
                    sel.alias = Some(alias.into_iden());
                }
            };
        });
        self
    }

    /// Selects extra Entity and returns it together with the Entity from `Self`
    pub fn select_also<F>(mut self, _: F) -> SelectTwo<E, F>

View on GitHub (pinned to e29bcd1b41)

Solutions

Name the concrete column inside the AsEnum expression instead of an asterisk
Apply the enum cast only to a specific column: Expr::col(col).as_enum(...)
Build the aliased query without AsEnum on wildcard selects

Example fix

// before
Expr::asterisk().as_enum(MyEnum)
// after
Expr::col((entity, my_col)).as_enum(MyEnum)

Defensive patterns

Strategy: validation

Validate before calling

fn as_enum_inner_is_column(expr: &SimpleExpr) -> bool {
    matches!(expr, SimpleExpr::AsEnum(_, inner)
        if matches!(inner.as_ref(), SimpleExpr::Column(c) if c.column().is_some()))
}

Type guard

fn enum_wrapped_column(expr: &SimpleExpr) -> bool {
    match expr {
        SimpleExpr::AsEnum(_, inner) => matches!(inner.as_ref(), SimpleExpr::Column(c) if c.column().is_some()),
        _ => false,
    }
}

Try / catch

// panics are not catchable; guard before building
debug_assert!(as_enum_inner_is_column(&expr), "AsEnum must wrap a concrete column");

Prevention

Wrap only named columns in .as_enum(...), never asterisk
Review generated select exprs for wildcard casts
Keep enum-cast helpers constrained to typed columns

When it happens

Trigger: Using select_also/select_with/select_two_required/left_join_linked where a select expression is AsEnum wrapping an asterisk Column — e.g. casting a wildcard select to an enum instead of naming a real column.

Common situations: Hand-built select lists that combine .as_enum(...) casts with select_all-style wildcards; copy-pasted select expressions never narrowed to a concrete column.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of SeaQL/sea-orm@e29bcd1b41 (2026-09-10). Data as JSON: /api/errors/132f43d4bdbfa0db. Report an issue: GitHub.