Implement LWG 3065: Make path operators friends.

This prevents things like:

using namespace std::filesystem;
auto x = L"a/b" == std::string("a/b");

3 files changed, 63 insertions, 1 deletions

diff --git a/libcxx/test/std/input.output/filesystems/class.path/path.nonmember/append_op.fail.cpp b/libcxx/test/std/input.output/filesystems/class.path/path.nonmember/append_op.fail.cpp
new file mode 100644
index 00000000000..e0b3a959c29
--- /dev/null
+++ b/libcxx/test/std/input.output/filesystems/class.path/path.nonmember/append_op.fail.cpp
@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// <filesystem>
+
+#include "filesystem_include.hpp"
+
+using namespace fs;
+
+struct ConvToPath {
+  operator fs::path() const {
+    return "";
+  }
+};
+
+int main() {
+  ConvToPath LHS, RHS;
+  (void)(LHS / RHS); // expected-error {{invalid operands to binary expression}}
+}
\ No newline at end of file
diff --git a/libcxx/test/std/input.output/filesystems/class.path/path.nonmember/append_op.pass.cpp b/libcxx/test/std/input.output/filesystems/class.path/path.nonmember/append_op.pass.cpp
index 09498bf2135..2a291d61da7 100644
--- a/libcxx/test/std/input.output/filesystems/class.path/path.nonmember/append_op.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/class.path/path.nonmember/append_op.pass.cpp
@@ -20,7 +20,6 @@
 #include "test_macros.h"
 #include "filesystem_test_helper.hpp"
 
-
 // This is mainly tested via the member append functions.
 int main()
 {
@@ -29,4 +28,7 @@ int main()
   path p2("def");
   path p3 = p1 / p2;
   assert(p3 == "abc/def");
+
+  path p4 = p1 / "def";
+  assert(p4 == "abc/def");
 }
diff --git a/libcxx/test/std/input.output/filesystems/class.path/path.nonmember/comparison_ops.fail.cpp b/libcxx/test/std/input.output/filesystems/class.path/path.nonmember/comparison_ops.fail.cpp
new file mode 100644
index 00000000000..00eafe532d0
--- /dev/null
+++ b/libcxx/test/std/input.output/filesystems/class.path/path.nonmember/comparison_ops.fail.cpp
@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// <filesystem>
+
+
+#include "filesystem_include.hpp"
+
+using namespace fs;
+
+struct ConvToPath {
+  operator fs::path() const {
+    return "";
+  }
+};
+
+int main() {
+  ConvToPath LHS, RHS;
+  (void)(LHS == RHS); // expected-error {{invalid operands to binary expression}}
+  (void)(LHS != RHS); // expected-error {{invalid operands to binary expression}}
+  (void)(LHS < RHS); // expected-error {{invalid operands to binary expression}}
+  (void)(LHS <= RHS); // expected-error {{invalid operands to binary expression}}
+  (void)(LHS > RHS); // expected-error {{invalid operands to binary expression}}
+  (void)(LHS >= RHS); // expected-error {{invalid operands to binary expression}}
+}
\ No newline at end of file