Infer generic types based on properties

[DavidKDeutsch]

This may be a duplicate of #7234 and/or #3812, but I don't know enough about the internals of TypeScript to know for sure. Let's say I have the following:

interface MyInfo<T> {
   data: T;
}

class Foo {
   x: number;
} 

let fooInfos: MyInfo<Foo>[];
let objectInfos: MyInfo<Object>[];

for (let info of objectInfos) {
   if (info.data instanceof Foo) {
       fooInfos.push(info); // should infer that info is MyInfo<Foo>, but it doesn't
   }
} 

In this case, the compiler still thinks info is of type MyInfo<Object> instead of MyInfo<Foo>, whereas I would expect it to be able to properly infer the type.

[mhegazy]

this is a duplicate of #3812.