phantom state valid

const std = @import("std");
~event open-file {}
| opened *std.fs.File<open>
~proc open-file|zig {
    std.debug.print("File opened\n", .{});
    const allocator = std.heap.page_allocator;
    const f = allocator.create(std.fs.File) catch unreachable;
    return .{ .opened = f };
}
~event close-file { file: *std.fs.File<open> }
| closed *std.fs.File<closed>
~proc close-file|zig {
    std.debug.print("File closed\n", .{});
    return .{ .closed = file };
}
~open-file()
| opened o |> close-file(file: o)
    | closed _ |> _