swc-project/swc · error

as_bool() for JSXText

Error message

as_bool() for JSXText

What it means

An unreachable!() arm in as_bool (swc_ecma_utils lib.rs:3028). The function statically evaluates which literals are truthy (numbers, bigints, bools, strings, null, regex...); JSXText is not a boolean-context literal — JSX text used in an expression position has no truthiness semantics that swc models, so reaching this arm means a JSXText literal was fed to as_bool, a case the evaluator deliberately refuses. The JSXText literal is the input at fault.

Source

Thrown at crates/swc_ecma_utils/src/lib.rs:3028

        Expr::Unary(UnaryExpr {
            op: op!("void"), ..
        }) => Known(false),

        Expr::Lit(ref lit) => {
            return (
                Pure,
                Known(match *lit {
                    Lit::Num(Number { value: n, .. }) => is_truthy_number(n),
                    Lit::BigInt(ref v) => v
                        .value
                        .to_string()
                        .contains(|c: char| matches!(c, '1'..='9')),
                    Lit::Bool(b) => b.value,
                    Lit::Str(Str { ref value, .. }) => !value.is_empty(),
                    Lit::Null(..) => false,
                    Lit::Regex(..) => true,
                    Lit::JSXText(..) => unreachable!("as_bool() for JSXText"),
                    #[cfg(swc_ast_unknown)]
                    _ => return (Pure, Unknown),
                }),
            );
        }

        //TODO?
        _ => Unknown,
    };

    if expr.may_have_side_effects(ctx) {
        (MayBeImpure, val)
    } else {
        (Pure, val)
    }
}

fn cast_to_number(expr: &Expr, ctx: ExprCtx) -> (Purity, Value<f64>) {

View on GitHub (pinned to 5176682b65)

Solutions

1. Check the expression kind before calling as_bool and skip JSXText-bearing expressions
2. Return Known(true)/Unknown for JSXText instead of panicking if a conservative answer is acceptable
3. Avoid feeding JSX-containing ASTs into boolean static-evaluation passes

When it happens

Trigger: Thrown at crates/swc_ecma_utils/src/lib.rs:3028 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of swc-project/swc@5176682b65 (2026-08-17). Data as JSON: /api/errors/e74f198fb0e68f7b. Report an issue: GitHub.