What is the Swift syntax “ .bar” called?

Question

Swift has this handy syntax:

enum Foo {
    case bar
    case baz
}


func hoge(foo: Foo) {
}


hoge(foo: .bar) //          


        

Answer 1

It is called an implicit member expression. From the grammar section of the language guide:

An implicit member expression is an abbreviated way to access a member of a type, such as an enumeration case or a type method, in a context where type inference can determine the implied type. It has the following form:

.member name

For example:

var x = MyEnumeration.someValue
x = .anotherValue