Generated extension functions don't compile

[epabst]

Example:

/// <reference path="../../testDefinitelyTyped/DefinitelyTyped/jquery/jquery.d.ts" />

interface JQuery {
    foo()
    bar
    [prop: string]: number;
    someField: string;
    optionalField?: any;
    (resourceId:string, hash?:any, callback?:Function): void;
}

results in:

external fun JQuery.foo(): Unit = definedExternally
external var JQuery.bar: Any get() = definedExternally; set(value) = definedExternally
@nativeGetter
external operator fun JQuery.get(prop: String): Number? = definedExternally
@nativeSetter
external operator fun JQuery.set(prop: String, value: Number): Unit = definedExternally
external var JQuery.someField: String get() = definedExternally; set(value) = definedExternally
external var JQuery.optionalField: Any? get() = definedExternally; set(value) = definedExternally
@nativeInvoke
external operator fun JQuery.invoke(resourceId: String, hash: Any? = definedExternally /* null */, callback: Function<*>? = definedExternally /* null */): Unit = definedExternally

which fails with compile error "Declaration of such kind (extension function) cant be external", etc.
It should be:

fun JQuery.foo(): Unit { this.asDynamic().foo() }
var JQuery.bar: Any get() = this.asDynamic().bar; set(value) { this.asDynamic().bar = value }
operator fun JQuery.get(prop: String): Number? { return this.asDynamic().get(prop) }
operator fun JQuery.set(prop: String, value: Number): Unit { this.asDynamic().set(prop, value) }
var JQuery.someField: String get() = this.asDynamic().someField; set(value) { this.asDynamic().someField = value }
var JQuery.optionalField: Any? get() = this.asDynamic().optionalField; set(value) { this.asDynamic().optionalField = value }
operator fun JQuery.invoke(resourceId: String, hash: Any? = null, callback: Function<*>? = null): Unit { this.asDynamic().invoke(resourceId, hash, callback) }