Exploring how to return a reader with Zig

file_reader.zig

const std = @import("std");
// fails with compile error
pub fn fileReader() !type {
    var file = try std.fs.cwd().openFile("./lines.csv", .{});
    defer file.close();
    var buf_reader = std.io.bufferedReader(file.reader());
    return buf_reader.reader();
}

pub fn main() !void {
    _ = fileReader();
}

out_build_fail.txt

/usr/local/Cellar/zig/0.9.1/lib/zig/std/os.zig:1456:20: error: unable to evaluate constant expression
        const rc = openat_sym(dir_fd, file_path, flags, mode);
                   ^
/usr/local/Cellar/zig/0.9.1/lib/zig/std/fs.zig:1025:27: note: called from here
            try os.openatZ(self.fd, sub_path, os_flags, 0);
                          ^
/usr/local/Cellar/zig/0.9.1/lib/zig/std/fs.zig:958:30: note: called from here
        return self.openFileZ(&path_c, flags);
                             ^
./file_reader.zig:4:41: note: called from here
    var file = try std.fs.cwd().openFile("./lines.csv", .{});
                                        ^
./file_reader.zig:11:19: note: called from here
    _ = fileReader();
                  ^
./file_reader.zig:10:21: note: called from here
pub fn main() !void {