[SPOILERS] X and Y pre-release Leaks and Rumours thread

How are dual type attacks supposed to work? If you use a move and one of the types of the attack does not affect the defending pokemon, what happens? Does all damage get nullified? Half? how will it work.

I'm assuming only the main typing takes precedence and is affected by certain elements, like STAB and non-effectiveness (ex: Fighting/Normal-type moves have no effect on Ghost-types).

[SPOILER=So let's say Hawlucha tries to use Flying Press on a Ghost-type...] I don't think anything will occur and the pseudo-Flying-typing will have no effect.

I wonder if GameFreak thought this through, and made it so no attack can be more than 4x effective/0.25x effective against a Pokemon. I feel like 8x effective is crazy overkill.