fs: add and test for DirectoryNotEmpty error variant

src/helpers.rs

@@ -490,6 +490,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 TimedOut => "ETIMEDOUT",
                 AlreadyExists => "EEXIST",
                 WouldBlock => "EWOULDBLOCK",
+                DirectoryNotEmpty => "ENOTEMPTY",
                 _ => {
                     throw_unsup_format!(
                         "io error {:?} cannot be translated into a raw os error",

src/lib.rs

@@ -5,6 +5,7 @@
 #![feature(try_blocks)]
 #![feature(let_else)]
 #![feature(bool_to_option)]
+#![feature(io_error_more)]
 #![warn(rust_2018_idioms)]
 #![allow(clippy::cast_lossless)]
 

tests/run-pass/fs.rs

@@ -2,6 +2,7 @@
 // compile-flags: -Zmiri-disable-isolation
 
 #![feature(rustc_private)]
+#![feature(io_error_more)]
 
 extern crate libc;
 
@@ -380,6 +381,8 @@ fn test_directory() {
     let mut file_names = dir_iter.map(|e| e.unwrap().file_name()).collect::<Vec<_>>();
     file_names.sort_unstable();
     assert_eq!(file_names, vec!["test_file_1", "test_file_2"]);
+    // Deleting the directory should fail, since it is not empty.
+    assert_eq!(ErrorKind::DirectoryNotEmpty, remove_dir(&dir_path).unwrap_err().kind());
     // Clean up the files in the directory
     remove_file(&path_1).unwrap();
     remove_file(&path_2).unwrap();