Strict interface implementation

[Alacrit]

TypeScript Version: 2.6.1

Code

interface IEmpty {
}

interface IParam {
    param: number;
}

interface IFn<T> {
    fn(param: T): void;
}

class MyClass implements IFn<IParam> {
    // Wrong param interface implementation (only if empty)
    // Wrong return type implementation
    // But no compiler errors - WHY? How to avoid this?
    fn(param: IEmpty): string {
        return 'fnResult';
    }
}

Expected behavior:
Compiler error. Or any way to force compiler to do EmptyParamTypeCheck and VoidReturnTypeCheck.

Actual behavior:
No errors.

[RyanCavanaugh]

Both your questions are answered in the FAQ https://github.com/Microsoft/TypeScript/wiki/FAQ