support method provider

[sin5th]

Is your feature request related to a problem? Please describe.

I used to write type method instead of a single NewXxx. eg:

// declare NewDog method, which belong to type Animals

type Animals struct{}

func NewAnimals() *Animals {
	return &Animals{}
}

type Dog struct{}

func (f *Animals) NewDog() *Dog {
	return &Dog{}
}

frustrated when I want to use it as wire provider, I got unknown pattern error. eg:

// wire.go

//+build wireinject
//go:generate wire

func InitDog() *animals.Dog {
	panic(wire.Build(
		animals.NewAnimals,
		(*animals.Animals).NewDog, // this line will trigger error
	))
}

Describe the solution you'd like

I want the above usage could be work. Generated code should looks like:

// wire_gen.go

func InitDog() *animals.Dog {
	animalsAnimals := animals.NewAnimals()
	dog := (*animals.Animals).NewDog(animalsAnimals)
	return dog
}