error: unsupported operation: `open` not available when isolation is enabled
   |
   = help: pass the flag `-Zmiri-disable-isolation` to disable isolation;
   = help: or pass `-Zmiri-isolation-error=warn` to configure Miri to return an error code from isolated operations (if supported for that operation) and continue with a warning
           
   = note: inside closure at rustc_src/src/sys/PLATFORM/fs.rs:LL:CC
   = note: inside `std::sys::PLATFORM::cvt_r::<i32, [closure@std::sys::PLATFORM::fs::File::open_c::{closure#0}]>` at rustc_src/src/sys/PLATFORM/mod.rs:LL:CC
   = note: inside `std::sys::PLATFORM::fs::File::open_c` at rustc_src/src/sys/PLATFORM/fs.rs:LL:CC
   = note: inside `std::sys::PLATFORM::fs::File::open` at rustc_src/src/sys/PLATFORM/fs.rs:LL:CC
   = note: inside `std::fs::OpenOptions::_open` at rustc_src/src/fs.rs:LL:CC
   = note: inside `std::fs::OpenOptions::open::<&std::path::Path>` at rustc_src/src/fs.rs:LL:CC
   = note: inside `std::fs::File::open::<&str>` at rustc_src/src/fs.rs:LL:CC
note: inside `main` at $DIR/isolated_file.rs:LL:CC
  --> $DIR/isolated_file.rs:LL:CC
   |
LL |     let _file = std::fs::File::open("file.txt").unwrap();
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace

error: aborting due to previous error