I will, and thanks.

DOES it fall under the warning of 'don't use this if you want 100%
compiler-neutrality?


Andrew Wetmore
Assistant VP, Marketing and Publicity, The ASF <http://aparch.org>
Editor-Writer, Infra team, The ASF

Editor, moosehousepress.com


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On Mon, Jan 26, 2026 at 4:04 PM Josh Tynjala <[email protected]>
wrote:

> I don't think I added it to the right sidebar. Go ahead and add it, if you
> like.
>
> I added it to the list of "New ActionScript language features" on the AS3
> page, though.
>
> --
> Josh Tynjala
> Bowler Hat LLC
> https://bowlerhat.dev/
>
>
> On Mon, Jan 26, 2026 at 11:58 AM Andrew Wetmore <[email protected]>
> wrote:
>
> > This is a great add.
> >
> > Did you include this new page in the index of site pages that appears on
> > the right? I don't see it. I can add it, if you like.
> >
> > And does this feature fall into the category of "New ActionScript
> language
> > features in Royale" on https://apache.github.io/royale-docs/features/as3
> ?
> > These come with a caution not to use them if you want your app to be 100%
> > compiler-neutral.
> >
> > a
> >
> >
> > Andrew Wetmore
> > Assistant VP, Marketing and Publicity, The ASF <http://aparch.org>
> > Editor-Writer, Infra team, The ASF
> >
> > Editor, moosehousepress.com
> >
> >
> > <
> >
> https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail
> > >
> > Virus-free.www.avast.com
> > <
> >
> https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail
> > >
> > <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
> >
> > On Tue, Jan 20, 2026 at 4:33 PM Harbs <[email protected]> wrote:
> >
> > > Thank you Josh!!!
> > >
> > > This is probably my #1 feature I’ve been missing in ActionScript.
> > >
> > > This will do a world of good for type safety and being able to express
> > > required types!
> > >
> > > I’m looking forward to making use of this!
> > >
> > > Harbs
> > >
> > > > On Jan 20, 2026, at 10:29 PM, Josh Tynjala <
> [email protected]>
> > > wrote:
> > > >
> > > > Hi folks,
> > > >
> > > > I just wanted to take a moment to highlight a new ActionScript
> language
> > > > feature that I recently implemented in Royale's compiler: Function
> type
> > > > expressions. Or perhaps you might call them strict function types.
> > > >
> > > > Basically, instead of using the Function type, like this:
> > > >
> > > > var validate:Function;
> > > >
> > > > You can define the function signature as a type, like this (The
> syntax
> > is
> > > > pretty similar to TypeScript's):
> > > >
> > > > var validate:(input:String)=>Boolean;
> > > >
> > > > And then, the compiler can check for mismatches. The following
> > assignment
> > > > will fail:
> > > >
> > > > var validate:(input:String)=>Boolean =
> > function(input:ByteArray):Boolean
> > > {
> > > > return false; }
> > > >
> > > > It should give the following error:
> > > >
> > > > Error: Implicit coercion of a value of type
> (input:ByteArray)=>Boolean
> > to
> > > > an unrelated type (input:String)=>Boolean.
> > > >
> > > > The syntax supports optional parameters and rest parameters. Optional
> > > > parameters would be equivalent to parameters that have a default
> value
> > > in a
> > > > regular function signature. However, you don't need to specify the
> > > default
> > > > value in the function type expression (assigned functions are allowed
> > to
> > > > have different default values or to use rest instead), and you may
> use
> > > the
> > > > ? token to indicate that a specific parameter is optional.
> > > >
> > > > var func:(s?:String, ...rest):void;
> > > >
> > > > You can even nest function type expressions.
> > > >
> > > > var action:(callback:(result:Object)=>void):void;
> > > >
> > > > I've created some documentation to help folks get started:
> > > >
> > > >
> > https://apache.github.io/royale-docs/features/as3/strict-function-types
> > > >
> > > > --
> > > > Josh Tynjala
> > > > Bowler Hat LLC
> > > > https://bowlerhat.dev/
> > >
> > >
> >
>

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