Use case 1: Form

    typedef User = struct(
        String* email,
        String* password,
    );

    typedef Form[User] = 

Use case 2: Custom control
    
    // editable data, with "instant-apply"
    namespace DateEditor = (
        typedef = struct(
            InstantEditableData[Date] base,
        )
        
        (DateEditor* this) new(Date* date) {
            this = alloc(DateEditor);
            this.init(date);
        }
        
        (DateEditor* this) init(DateEditor* this, Date* date) {
            this.base.init();
            this.date = date;
        }
        
        (DateEditor*? this) new(DateEditor*? target, Date* date) {
            this = (target != null ? this : alloc(DateEditor));
            this.base.init(this);
            this.date = date;
        }
    )
    
    

Use case 2: