type-alias

问题 This is a follow up question of: In scala, how to make type class working for Aux pattern? Considering the following example: trait Base { type Out def v: Out } object Base { type Aux[T] = Base { type Out = T } type Lt[T] = Base { type Out <: T } class ForH() extends Base { final type Out = HNil override def v: Out = HNil } object ForH extends ForH } trait TypeClasses { class TypeClass[B] def summon[B](b: B)(implicit ev: TypeClass[B]): TypeClass[B] = ev } object T1 extends TypeClasses {

问题 Abstract member method is illegal in a singleton object scala> object Foo { | def g: Int | } def g: Int ^ On line 2: error: only traits and abstract classes can have declared but undefined members as is abstract value member scala> object Foo { | val x: Int | } val x: Int ^ On line 2: error: only traits and abstract classes can have declared but undefined members however abstract type member is legal in a singleton object scala> object Foo { | type A | } object Foo so clearly the sense in

问题 Abstract member method is illegal in a singleton object scala> object Foo { | def g: Int | } def g: Int ^ On line 2: error: only traits and abstract classes can have declared but undefined members as is abstract value member scala> object Foo { | val x: Int | } val x: Int ^ On line 2: error: only traits and abstract classes can have declared but undefined members however abstract type member is legal in a singleton object scala> object Foo { | type A | } object Foo so clearly the sense in

问题 I was wondering how could one declare a typed-function array in TypeScript. For instance, say I have a field which can hold a function that has no arguments and returns void: private func: () => void; Now, say I wanted a field which can hold an array of such functions: private funcs: () => void []; This is obviously the wrong way to do what I intended since the compiler considers this to be a function which returns an array of voids. Trying to isolate the inline prototype declaration with

问题 I was wondering how could one declare a typed-function array in TypeScript. For instance, say I have a field which can hold a function that has no arguments and returns void: private func: () => void; Now, say I wanted a field which can hold an array of such functions: private funcs: () => void []; This is obviously the wrong way to do what I intended since the compiler considers this to be a function which returns an array of voids. Trying to isolate the inline prototype declaration with

问题 Here is a simple example: trait Base { type Out def v: Out } object Base { type Aux[T] = Base { type Out = T } class ForH() extends Base { type Out = HNil override def v: Out = HNil } object ForH extends ForH } class TypeClass[B] trait TypeClassLevel1 { def summon[B](b: B)(implicit ev: TypeClass[B]): TypeClass[B] = ev } object TypeClass extends TypeClassLevel1 { implicit def t1: TypeClass[Base.Aux[HNil]] = new TypeClass[Base.Aux[HNil]] implicit def t2: TypeClass[Int] = new TypeClass[Int] } it

来源： https://stackoverflow.com/questions/64226096/why-type-alias-is-allowed-as-name-of-variable

来源： https://stackoverflow.com/questions/60155508/using-type-alias-of-class-scope-when-can-usages-in-methods-precede-the-type

来源： https://stackoverflow.com/questions/55622136/swift-what-is-the-difference-between-a-typealias-and-an-associatedtype-with-a-v

来源： https://stackoverflow.com/questions/55622136/swift-what-is-the-difference-between-a-typealias-and-an-associatedtype-with-a-v