Index: libcxx/include/filesystem
===================================================================
--- libcxx/include/filesystem
+++ libcxx/include/filesystem
@@ -259,6 +259,7 @@
 #include <version>
 
 #if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+# include <cassert> // for unimplemented path functions
 # include <locale>
 # include <iomanip> // for quoted
 #endif
@@ -969,10 +970,14 @@
 #if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
   // TODO Implement locale conversions.
   template <class _Source, class = _EnableIfPathable<_Source, void> >
-  path(const _Source& __src, const locale& __loc, format = format::auto_format);
+  path(const _Source& __src, const locale& __loc, format = format::auto_format) {
+    assert(false && "locale conversions are unimplemented");
+  }
   template <class _InputIt>
   path(_InputIt __first, _InputIt _last, const locale& __loc,
-       format = format::auto_format);
+       format = format::auto_format) {
+         assert(false && "locale conversions are unimplemented");
+       }
 #endif
 
   _LIBCPP_INLINE_VISIBILITY