Add an IO::Path.dir-with-entries method

Checking whether a directory has entries in it, can be checked by
doing e.g. an "if .dir.head {".  However, this will leak resources
as the iterator that runs "dir" will never be finished, and thus
the underlying directory handle will also never be closed.

Alternately, doing an "if dir.elems {" *would* close the underlying
directory handle, but possibly after doing a lot of work if the
directory in question actually contains *many* entries.

This method will return a Bool that will indicate whether the IO::Path
has any entries in it (:test to give a tester, default to "none(<. ..>)").
It will stop as soon as it finds a matching entry, close the directory
handle, and return.

src/core.c/IO/Path.pm6

@@ -842,6 +842,28 @@ my class IO::Path is Cool does IO {
         }
     }
 
+    proto method dir-with-entries(|) {*}
+    multi method dir-with-entries(IO::Path:D: --> Bool:D) {
+        my $handle := nqp::opendir(self.absolute);
+        nqp::while(
+          (my str $entry = nqp::nextfiledir($handle))
+            && (nqp::iseq_s($entry,'.') || nqp::iseq_s($entry,'..')),
+          nqp::null()
+        );
+        nqp::closedir($handle);
+        nqp::hllbool(nqp::chars($entry))
+    }
+    multi method dir-with-entries(IO::Path:D: :$test! --> Bool:D) {
+        my $handle := nqp::opendir(self.absolute);
+        nqp::while(
+          (my str $entry = nqp::nextfiledir($handle))
+            && !$test.ACCEPTS($entry),
+          nqp::null()
+        );
+        nqp::closedir($handle);
+        nqp::hllbool(nqp::chars($entry))
+    }
+
     method CHECKSUM(IO::Path:D: --> Str:D) is implementation-detail {
         my \slurped := self.slurp(:enc<iso-8859-1>);
         nqp::istype(slurped,Failure)