narrowing an undefined | A property not working anymore

[zpdDG4gta8XKpMCd]

nightly build August 5, 2016

function noUnnecessaryTypeAnnotations(node: ts.Node, checker: ts.TypeChecker): Issue | void {
    if (isVariableDeclaration(node)) {
        if (node.initializer !== undefined && node.type !== undefined) {
            node.initializer; // <-- expected: Expression; actual: Expression | undefined
        }
   }
}

[ahejlsberg]

The issue here is that the checker thinks node.type !== undefined might be a discriminant type guard, so it resets other type guards for properties of the form node.xxx. A workaround would be to reverse the two type guards (but of course you'll then have the same problem for node.type).