Declaration file not generated properly when extending from a function that returns a constructor signature.

[rzvc]

TypeScript Version: 2.4.0-dev.20170503

Code

class SomeClass
{
}

interface IFace
{
}

class Derived extends getClass<IFace>()
{
}

function getClass<T>() : new() => T
{
	return SomeClass as any;
}

To compile: tsc test.ts --declaration

Expected output:

declare class SomeClass {
}
interface IFace {
}
declare class Derived extends getClass<IFace>() {
}
declare function getClass<T>(): new () => T;

Actual output:

declare class SomeClass {
}
interface IFace {
}
declare class Derived extends IFace {
}
declare function getClass<T>(): new () => T;

The problem here is that IFace is not a class, so it can't be extended, which is why the original declaration should be used instead. If it was a class, the output would be perfectly valid.