Clarify the status of "pairup"

And add tests

README.md

@@ -277,6 +277,11 @@ pairs
 
 **Status**: an optimized version of the [`.pairs`](https://docs.raku.org/type/List#routine_pairs) method has been implemented.
 
+pairup
+------
+
+**Status**: the nature of the [`pairup`](https://docs.raku.org/type/Any#method_pairup) method basically makes it impossible to hyper. Therefore, **no** specific hypering logic has been added for this method.
+
 permutations
 ------------
 

doc/ParaSeq.rakudoc

@@ -343,6 +343,13 @@ B<Status>: an optimized version of the
 L<C<.pairs>|https://docs.raku.org/type/List#routine_pairs> method
 has been implemented.
 
+=head2 pairup
+
+B<Status>: the nature of the
+L<C<pairup>|https://docs.raku.org/type/Any#method_pairup>  method
+basically makes it impossible to hyper.  Therefore, B<no> specific
+hypering logic has been added for this method.
+
 =head2 permutations
 
 L<C<.permutations>|https://docs.raku.org/type/List#routine_permutations>

lib/ParaSeq.rakumod

@@ -1518,7 +1518,7 @@ class ParaSeq does Sequence {
     }
 
     multi method pairup(ParaSeq:D:) {
-        self!pass-the-chain: self.Seq.pairup.iterator
+        self!pass-the-chain: self.List.pairup.iterator
     }
 
     proto method permutations(|) {*}

t/39-pairup.rakutest

@@ -0,0 +1,17 @@
+use Test;
+use ParaSeq;
+
+plan 4;
+
+my constant $elems    = 200000;
+my constant @list     = (^$elems).List;
+my constant @pairedup = @list.pairup.List;
+my constant $batch    = 16;
+
+for 1, ParaSeq.default-degree {
+    my $seq := @list.&hyperize($batch, $_).pairup;
+    isa-ok $seq, $_ == 1 ?? Seq !! ParaSeq;
+    is-deeply $seq.List, @pairedup, ".pairup with degree = $_";
+}
+
+# vim: expandtab shiftwidth=4