Proposed resolution:

This wording is relative to N4582.

1. Change [fs.filesystem.syn] as indicated:

   namespace std::filesystem {
     […]
   
     void permissions(const path& p, perms prms);
     void permissions(const path& p, perms prms, error_code& ec) noexcept;
   
     […]
   }
   

2. Change [fs.op.permissions] as indicated:

   void permissions(const path& p, perms prms);
   void permissions(const path& p, perms prms, error_code& ec) noexcept;
   

   -1- Requires: !((prms & perms::add_perms) != perms::none && (prms & perms::remove_perms) != perms::none).

[ 2016-06 Oulu ]

Moved to P0/Ready during issues prioritization.

Friday: status to Immediate

Currently the signatures for permissions are:

void permissions(const path& p, perms prms);
void permissions(const path& p, perms prms, error_code& ec) noexcept;

However both overloads have a narrow contract since due to the requires clause:

Requires: !((prms & perms::add_perms) != perms::none && (prms & perms::remove_perms) != perms::none).

For this reason I believe the second overload of permissions should not be marked noexcept.