I bumped into this interesting behavior around unsigned types. At first I was confused why UInt doesn’t extend Number, but as I was experimenting, it got weirder. It sometimes is a Number (see case c below) and sometimes isn’t (see case d)?!
val a: Int = 12
a is Number // true
val b: UInt = 12u
b is Number // doesn't compile, `Incompatible types: Number and UInt`
val c: UInt = 12u
(c as Any) is Number // true, Idea says "No cast needed"
val d: Any = 12u
d is Number // false
I guess this is partly legacy of Java, which doesn’t have unsigned types, and partly effect of UInt being value class. I’m curious if someone has a deeper explanation.
Kotlin does a pretty good job in general, and these bugs are so difficult to track down and frustrating when encountered.
Jetbrains took on a pretty monumental task targeting JVM, native, and other platforms. I really want to see them succeed.