Support for type declarations and Intersection types

[markwpearce]

It would be nice be able to support "mixins" to interfaces...

Basically, some way of being able to say this interface is composed of these other interfaces:

Eg. source/mixins/alpha.bs:

interface AlphaM
   alpha as boolean
end interface

sub initAlpha()
   m.alpha = true
end sub

components/MyComponent.xml

<component name="MyComponent" extends="Group">
    <script type="text/brightscript" uri="pkg:/source/mixins/alpha.bs" />
    <interface>
       <field id="text" type="string" />
    </interface>
</component>

components/MyComponent.bs

typecast m as MyComponentM

interface MyComponentM
   top as roSGNodeMyComponent
   include AlphaM ' not married to this syntax, but this is the magic
end interface

sub init()
   initAlpha()
  print m.alpha ' this is known to be a boolean
end sub

[TwitchBronBron]

For most basic cases (including the one you just listed), this would just be interfaces extending other interfaces:

interface MyComponentM extends AlphaM
   top as roSGNodeMyComponent
end interface

However, for multiple extension, I think we should do it how typescript does, with a type statement and type unions:

type ManyComponents = MyComponentM & AlphaM & roSGNodePoster

This would be even nicer if we eventually add inline interface types, because then you wouldn't have to name them ahead of time (not sure about the syntax, but something like this?):

type ManyComponents = AlphaM & roSGNodePoster & {
    top as roSGNodeMyComponent
}

[markwpearce]

OK... Changing this topic to be "Support for type declarations and Intersection types"