OS2 interoperability

[RySah]

I think there's a big issue with interoperability between os2 and os, specifically os2.File and os.Handle, where other core packages e.g. terminal has no support for the os2 package. I think there should be some interoperability provided between the 2 packages in the API of os2 at least until we've perhaps completely migrated to os2.

From what i've seen in os2 and os, a simple function like this should work:

as_unsafe_os_handle :: #force_inline proc(f: ^os2.File) -> os.Handle { 
    return os.Handle(os2.fd(f))
} 

os.Handle on my version of odin (dev-2025-12-nightly:ac61f08), is simply an file descriptor/handle with no other metadata. Meaning by simply capturing the file descriptor/handle from the os2.File and casting it as an os.Handle, it should technically work.

I think this function could help indicate to developers who may not understand the differences between the 2 packages, that their code primarily using os2 can still use code primarily targeting the os package. I definitely see this practice being considered unsafe, seeing as the way os.Handle and os2.File are managed in memory are different, but it can help produce far more efficient code than the routes some developers may mistakenly take e.g:

import "core:os"
import "core:os/os2"
import "core:terminal"

is_std_terminal :: proc(f: ^os2.File) -> bool {
    if f == os2.stdout { return terminal.is_terminal(os.stdout) }
    else if f == os2.stderr { return terminal.is_terminal(os.stderr) }
    else if f == os2.stdin { return terminal.is_terminal(os.stdin) }
    else { return false } 
}

Could more efficiently become:

import "core:os/os2"
import "core:terminal"

// Function now omits branching, and can easily map any os2.File to an respective os.Handle, overall more optimized.
is_terminal :: #force_inline proc(f: ^os2.File) -> bool {
    return terminal.is_terminal(os2.as_unsafe_os_handle(f))
}

Additional Notes:

• The example functions above is untested, but based off the API's it should technically work.
• as_unsafe_os_handle has went under a very simple test of assert(as_unsafe_os_handle(os2.stdout) == os.stdout)