Offer completions for model properties when model extends another model

[bterlson]

Clear and concise description of the problem

model Foo {
  x: string;
  y: string;
}

model Bar extends Foo {
  // here I should get completions for members of Foo.
}

This would be very handy, especially when you are modelling complex data shapes with inheritance rather than templates.

Checklist

• Follow our Code of Conduct
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[RodgeFu]

it's also better to clarify these completions are for override scenario somehow so that they won't confuse people we are not using overrides.

[qiaozha]

I don't think currently we can override properties for now?

But for other usage like

model Bar extends Foo {
  z: Foo.x;
}

Maybe we should also consider offer completions for spread of alias or spread of models or other kinds of combination ?

[bterlson]

You can override, but the type you override with has to be a subtype of the base. So in your example, if you set x to "someString" it would work.

it's also better to clarify these completions are for override scenario somehow so that they won't confuse people we are not using overrides.

Can you say more about what the potential confusion is?

[RodgeFu]

Can you say more about what the potential confusion is?

I think it would be confusing for user who is new to typespec and not familiar with the property override feature. Like when I first look at the issue, I just wondered why the intellisense needs to suggest me with the properties of parent type? do i need to define them again in the subtype for things to work (like implement interface in ts)? i just didn't realize it's for override... (i guess it may also because i am used to c# and would think about override scenario only when I type override/new keyword...) thx