Test coverage for LWG-2682 filesystem::copy() won't create a symlin…

…k to a directory (#3827)

tests/std/tests/P0218R1_filesystem/test.cpp

@@ -2248,6 +2248,26 @@ void test_copy_symlink() {
     }
 }
 
+void test_copy_directory_as_symlink() {
+    const path dirpath{L"./test-lwg2682-dir"sv};
+    error_code ec;
+    create_directory(dirpath, ec);
+    EXPECT(good(ec));
+    try {
+        copy(dirpath, L"./symlink"sv, copy_options::create_symlinks);
+        EXPECT(false);
+    } catch (filesystem_error& e) {
+        EXPECT(e.code().value() == static_cast<int>(errc::is_a_directory));
+    }
+    {
+        error_code copy_ec;
+        copy(dirpath, L"./symlink"sv, copy_options::create_symlinks, copy_ec);
+        EXPECT(copy_ec.value() == static_cast<int>(errc::is_a_directory));
+    }
+    remove_all(dirpath, ec);
+    EXPECT(good(ec));
+}
+
 void equivalent_failure_test_case(const path& left, const path& right) {
     EXPECT(throws_filesystem_error([&] { EXPECT(!equivalent(left, right)); }, "equivalent", left, right));
 
@@ -3997,6 +4017,8 @@ int wmain(int argc, wchar_t* argv[]) {
 
     test_copy_symlink();
 
+    test_copy_directory_as_symlink(); // per LWG-2682
+
     test_conversions();
 
     test_file_size();