What's the point of having a lot of this kind of writing in the code?

[junmaqiang]

Checklist

• I have searched the issue tracker for open issues that relate to the same feature, before opening a new one.
• This issue only relates to a single feature. I will open new issues for any other features.

Is your feature request related to a problem?

var _ CanvasObject = (*Container)(nil)

var _ Dialog = (*dialog)(nil)

why write like this？

Is it possible to construct a solution with the existing API?

why write like this

Describe the solution you'd like to see.

why write like this

[andydotxyz]

This seems like a general question, probably better targetted as a discussion, converting

[andydotxyz]

It is to declare that a type conforms to an interface - so you get compile errors if the object fails to implement a method of the interface.
Normally in Fyne code you will see a comment with it like:

// Declare conformity with CanvasObject interface

[junmaqiang]

thank you, I Understood it now