Safety phase does not consider associated types when checking checked_cast

[Bobini1]

Am I doing something wrong or is this an error in the language?

import java.lang.Object
import java.lang.Integer


def main(): Unit =
    let t: Integer = Box.box(0x02000000);
    let _a: Object = checked_cast(t);
    ()

-- Safety Error -------------------------------------------------- T:\flix\test\src\Main.flix

>> Illegal checked cast: Attempt to cast a non-Java type to a Java type.

7 |     let _a: Object = checked_cast(t);
                         ^^^^^^^^^^^^^^^
                         illegal cast

From: Boxed[Int32]
To  : java.lang.Object

[magnus-madsen]

What are you trying to do? What's the bigger program / real context?

Ideally you should not be using checked/unchecked cast.

[mlutze]

~~Box[Int32] is not the same as Integer. You should use Integer.valueOf if you need to create a Java Integer for some reason.~~

[magnus-madsen]

Box[Int32] is not the same as Integer. You should use Integer.valueOf if you need to create a Java Integer for some reason.

I am unsure actually. I think its an associated type which is actually Integer.

[mlutze]

Box[Int32] is not the same as Integer. You should use Integer.valueOf if you need to create a Java Integer for some reason.

I am unsure actually. I think its an associated type which is actually Integer.

:O You're right!

[magnus-madsen]

@Bobini1 It seems there is a small bug in the compiler here. Nevertheless, casts should be rare, so it would be nice to know what the "real program" needs to do. Unless you are just experimenting?

[Bobini1]

@magnus-madsen I'm trying to call this method via Java interop: https://java-native-access.github.io/jna/4.2.0/com/sun/jna/Function.html#invoke-java.lang.Class-java.lang.Object:A-

In particular, I would like to try to use it to call __stdcall NtQueryDirectoryFile from ntdll.dll and CreateFileW from Kernel32.dll.

[magnus-madsen]

OK, you can use an unchecked cast for now: https://doc.flix.dev/unchecked-casts.html