谁能告诉我我错过了什么？谢谢.

let a = false
let b = false
let c = false
 
func test(a: Bool,_ b: Bool,_ c: Bool) {
    switch (a,b,c) {
    case (true,false,_):
        print("Moved left!!!")
    case (true,true,_):
        print("Moved right!!!")
    case (false,_,false):
        print("Moved up!!!")
    case (false,true):
        print("Moved down!!!")
    // Error: Switch must be exhaustive,consider adding a default clause.
    }
}
 
test(false,false)
test(false,true)
test(false,true)
test(true,false)
test(true,true)