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Description
immutable: 4.0.0-rc.10
ts: 3.2.2
function foo<T extends Object>(a: T): Record.Factory<T> {
return class extends Record(a) {} // typescript error
}Even though we have specified that T is, in fact, an object we get an error when passing a into Record.
You can cast to an object explicitly and
function foo<T extends Object>(a: T): Record.Factory<T> {
return class extends Record(<Object>a) {}
}The problem is that we loose type info inside the [ananomous] class. This becomes important when we try to extend a
class B { b: number = 1 }
function foo<T extends Object>(a: T): Record.Factory<T & B> {
const allArgs : T & B = _.extend(new B(), a)
return class extends Record(<Object>allArgs) {
// because we cast to Object we loose the type info
bar() { return this.b } // typescript error
}
}There are workarrounds for this in turn (public readonly b!: number) but ideally this should be covered by simply passing allArgs as it has type T & B, both of which we know to be objects.