[committed] libstdc++: Fix PSTL test iterators

[Jonathan Wakely]

These were fixed upstream by:
https://github.com/uxlfoundation/oneDPL/pull/534
https://github.com/uxlfoundation/oneDPL/pull/546

libstdc++-v3/ChangeLog:

        * testsuite/util/pstl/test_utils.h (ForwardIterator::operator++):
        Fix return type.
        (BidirectionalIterator::operator++): Likewise.
        (BidirectionalIterator::operator--): Likewise.
---

Tested x86_64-linux. Pushed to trunk.

 libstdc++-v3/testsuite/util/pstl/test_utils.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/libstdc++-v3/testsuite/util/pstl/test_utils.h 
b/libstdc++-v3/testsuite/util/pstl/test_utils.h
index 55b510098a04..9c61a7145f59 100644
--- a/libstdc++-v3/testsuite/util/pstl/test_utils.h
+++ b/libstdc++-v3/testsuite/util/pstl/test_utils.h
@@ -154,7 +154,7 @@ class ForwardIterator
     explicit ForwardIterator(Iterator i) : my_iterator(i) {}
     reference operator*() const { return *my_iterator; }
     Iterator operator->() const { return my_iterator; }
-    ForwardIterator
+    ForwardIterator&
     operator++()
     {
         ++my_iterator;
@@ -194,13 +194,13 @@ class BidirectionalIterator : public 
ForwardIterator<Iterator, IteratorTag>
     explicit BidirectionalIterator(Iterator i) : base_type(i) {}
     BidirectionalIterator(const base_type& i) : base_type(i.iterator()) {}
 
-    BidirectionalIterator
+    BidirectionalIterator&
     operator++()
     {
         ++base_type::my_iterator;
         return *this;
     }
-    BidirectionalIterator
+    BidirectionalIterator&
     operator--()
     {
         --base_type::my_iterator;
-- 
2.49.0