if (constantText != null) {
return new StringLiteral(new UntypedAtomicValue(constantText));
} else if (content instanceof ValueOf) {
return ((ValueOf)content).convertToCastAsString();
} else {
StringJoin fn = (StringJoin)SystemFunction.makeSystemFunction(
"string-join", new Expression[]{content, new StringLiteral(StringValue.EMPTY_STRING)});
CastExpression cast = new CastExpression(fn, BuiltInAtomicType.UNTYPED_ATOMIC, false);
ExpressionTool.copyLocationInfo(this, cast);
return cast;
}