chained generic mixins fail

TypeScript Version: 3.2.0-dev.201xxxxx

Search Terms: chained generic mixins

Code

type Constructor<T> = new(...args: any[]) => T;

interface XInterface {
    value: string;
 }

function make<T extends Constructor<any>>(Base: T) {
    return class extends Base implements XInterface {
        value = "Hello!"
    }
}

// Great. Works.
class _X1 extends make(Function) { hello() { this.value; }}

type _T1 = Constructor<HTMLElement>;

// Oops. But changing `make(Base)`, to `make(Base as _T1)` works perfectly, 
// which makes no sense.
function make2<T extends _T1>(Base: T) {
    return class extends make(Base) { }
}

Expected behavior:
Compile.

Actual behavior:
Type '{ new (...args: any[]): make.(Anonymous class); prototype: make.(Anonymous class); } & T' is not a constructor function type.

Start by reproducing the supplied chained generic mixin example with the reported TypeScript 3.2.0-dev version, then compare it with the variant using Base as _T1. Trace the compiler's handling of the returned constructor type; done means the original example compiles without the reported error.