键入缩写

类型缩写允许你在现有类型上创建别名，以便为它们提供更有意义的感官。

// Name is an alias for a string
type Name = string

// PhoneNumber is an alias for a string
type PhoneNumber = string

然后你可以像使用任何其他类型一样使用别名：

// Create a record type with the alias
type Contact = {
    Name : Name
    Phone : PhoneNumber }

// Create a record instance
// We can assign a string since Name and PhoneNumber are just aliases on string type
let c = {
    Name = "Foo"
    Phone = "00 000 000" }

printfn "%A" c

// Output
// {Name = "Foo";
// Phone = "00 000 000";}

小心，别名不检查类型的一致性。这意味着可以将两个目标相同类型的别名分配给彼此：

let c = {
    Name = "Foo"
    Phone = "00 000 000" }
let d = {
    Name = c.Phone
    Phone = c.Name }

printfn "%A" d

// Output
// {Name = "00 000 000";
// Phone = "Foo";}