$PropertyType fails on extended class

[nrabinowitz]

This is a:

• [x] Bug Report

Which concerns:

• [x] flow-runtime

---

What is the current behaviour?

I am trying to use $PropertyType to check the property of an extended class. The following code illustrates the issue:

class AbstractClass {
  	prop: any;
};

type ClassProp<C: AbstractClass> = $PropertyType<C, 'prop'>;

class ConcreteClass extends AbstractClass {
  	prop: number;
}

const i = 12;
(i: ClassProp<ConcreteClass>);

Running this example in the Try Flow-Runtime interface throws the following error: Can only intersect object types.

---

What is the expected behaviour?

Parity with Flow: The same code runs without errors in Flow

It also correctly errors on failures against the extended type.

---

Which package versions are you using?

Tried in the current Try Flow-Runtime interface, assuming this is v0.17.0