Is synecdoche a type of irony?
Synecdoche is to represent the whole through one if its parts or vice versa. Examples of this include saying "I like your wheels" when you are referring to the whole car, or "Australia won a gold medal in relay" when really it was a team of Australia who won the medal.
Irony is when a person states one thing while meaning the opposite or an event happens with opposite results from what is expected, often with humour. Examples of this include an "Always Open Hostel" which has a sign saying "Closed," or a person commenting on a stormy day, "What lovely weather."
As you can see, these are clearly dissimilar subjects.
I hope I helped!