E0032: Unknown Event

You tried to emit an event that hasn't been declared in any abi block.

Example

fn main() {
    emit Transfer(1, 2, 100);  // Error: unknown event `Transfer`
}

How to fix

Declare the event in an abi block before emitting it:

abi Events {
    event Transfer(from: i64, to: i64, amount: i64);
}

fn main() {
    emit Transfer(1, 2, 100);  // OK
}