Typings for Polymer.mixinBehavior() assume a concrete type

[kito99]

Description

The typings for Polymer.mixinBehavior() do not allow use of abstract classes.

Steps to Reproduce

Example:

class MyappView1 extends Polymer.mixinBehaviors([Polymer['AppLocalizeBehavior']], NowElements.BaseView) {
}

Where NowElements.BaseView is an abstract class that extends Polymer.Element.

Expected Results

Successful compilation and execution.

Actual Results

TypeScript compilation error:

Error:(8, 84) TS2345: Argument of type 'typeof BaseView' is not assignable to parameter of type 'new () => BaseView'.
  Cannot assign an abstract constructor type to a non-abstract constructor type.

Browsers Affected

All

Versions

master

What's a little frustrating about this is that the everything works fine if you change the type declaration to the following:

 function mixinBehaviors(behaviors: object|object[], klass: any): any;

Clearly this is a pretty unsafe type declaration, but since the code runs, it's clear that JavaScript has no problem using an abstract class; it's a TypeScript issue.

I'm not sure there's a good solution for this, given there is a TypeScript limitation: microsoft/TypeScript#5843, but I think it's worth discussion so we can at the very least say something in the docs.

[TimvdLippe]

It appears that the upstream TypeScript issue has been closed as [working as intended]: microsoft/TypeScript#5843 (comment) Not sure how we can resolve this issue.

[TimvdLippe]

Per https://stackoverflow.com/questions/12802317/passing-class-as-parameter-causes-is-not-newable-error I thought typeof T would work here, but sadly that did not work either as it is a generic type 😢

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically closed after being marked stale. If you're still facing this problem with the above solution, please comment and we'll reopen!