Multiple inheritance workarounds
Declaring a constructor on the same interface as the instance members doesn't really make much sense -- if you're going to pass in a type dynamically to use in a constructor, it's the static side of the class that would be restricted. What you would want to do is probably something like this:
interface Colorable { colorize(c: string): void;}interface Countable { count: number;}interface ColorCountable extends Colorable, Countable {}interface ColorCountableCreator { new(info: {color: string; count: number}): ColorCountable;}class ColorCounted implements ColorCountable { count: number; colorize(s: string) { } constructor(info: {color: string; count: number}) { // ... }}function makeThings(c: ColorCountableCreator) { var results: ColorCountable[]; for(var i = 0; i < 10; i++) { results.push(new c({color: 'blue', count: i})); } return results;}var items = makeThings(ColorCounted);console.log(items[0].count);See also How does typescript interfaces with construct signatures work?