[Strict null checks] Hoisted variables should be usable without assignment

[JannesMeyer]

TypeScript Version: 2.0.2 with strictNullChecks

Code

if (isMaximised) {
    var onClose = () => {
        /* code */ 
    };
}
console.log(onClose); // Error: Variable 'onClose' is used before being assigned

Expected behavior:
onClose should have the type () => void | undefined and be usable. In my opinion the warning about usage before assignment is only necessary when strictNullChecks is off.

Actual behavior:
onClose has the type () => void and it doesn't compile when being used.

[mhegazy]

the compiler could not guarantee that this variable is used before it was initialized. if your intention is to treat it as () => void | undefined add a type annotation.