@Override
    public ConfigExpression<I, O> simplifyOnce() {
      var in = input.simplifyOnce();
      if (in instanceof ConfigExpression.Const<?, ?> inConst) {
        return constOf(TypeConversion.convert(output.convertFrom(inConst.value), signature.out));
      } else if (in instanceof ConfigExpression.Cast<?, ?> cast && cast.output == output) {
        @SuppressWarnings("unchecked") ConfigExpression<I, ?> newIn = (ConfigExpression<I, ?>) cast.input;
        return cast(signature, newIn, output);
      } else {
        return new Cast<>(signature, input.simplifyOnce(), output);
      }
    }
An expression that converts the input to a desired output {@link DataType} at runtime.
planetiler-custommap/src/main/java/com/onthegomap/planetiler/custommap/expression/ConfigExpression.java