const FileOpenError = error{
    AccessDenied,
    OutOfMemory,
    FileNotFound,
};

const AllocationError = error{
    OutOfMemory,
};

test "coerce superset to subset" {
    foo(FileOpenError.OutOfMemory) catch {};
}

fn foo(err: FileOpenError) AllocationError {
    return err;
}

// test_error=not a member of destination error set