I don't think there is a "right" answer. Defaulting to bignum makes no more sense than defaulting to float for inputs "1" and "3" if the operation to be performed on the next line is division. Symbolic doesn't make sense all of the time either, what if it's a calculator app and the user enters "2*π", they probably don't want "2π" to be the result.

If we're going to try to find a "right" answer from a language view without knowing the exact program and use cases then the most reasonable compromise is likely "error" because types weren't specified on the constants or parsing functions.