I have a function that looks a bit like

func (c *Context) RegisterHandler(f interface{}) error {
    // Do lots of checking to make sure a function was passed in
    // and it's arguments all implement a specific interface
}

func consumer(a ConcreteTypeA, b ConcreteTypeB) {}

func main() {
    ...
    c.RegisterHandler(consumer)
}

which roughly boils down to

var a ConcreteTypeA
var b ConcreteTypeB
a.InitFromContext(c)
b.InitFromContext(c)
consumer(a, b)

Is there a way I can make that interface{} more specific without changing it’s behavior? If not I’m fairly happy with my solution. I just hope I can cut down on runtime checks and possible bugs being uncaught at compile time.

My current implementation looks pretty similar to above. I have tried to do something like

func (c *Context) RegisterHandler(f func (...InitFromContexter)) error {
    // Do lots of checking to make sure a function was passed in
    // and it's arguments all implement a specific interface
}

But that causes all the existing code to fail because it will only receive variadic functions