init do end
end
-var a: Object
-var a = new A
-var b = new B
+
+var a: Object = new A
+var b: Object = new B
(a isa A).output
(a isa Object).output
(not a isa B).output
-a = null
-(a isa A).output
-(a isa Object).output
-(a isa B).output
+(a isa nullable A).output
+(a isa nullable Object).output
+(not a isa nullable B).output
+var c: nullable Object = null
+(c isa A).output
+(c isa Object).output
+(c isa B).output
+(c isa nullable A).output
+(c isa nullable Object).output
+(c isa nullable B).output