Allow per-element comparison of string against non-string iterable (of char).

Test.

Author: ecatmur

include/boost/test/tools/collection_comparison_op.hpp

@@ -387,9 +387,9 @@ compare_collections( Lhs const& lhs, Rhs const& rhs, boost::type<op::GE<L, R> >*
 template<typename Lhs,typename Rhs>                                 \
 struct name<Lhs,Rhs,typename boost::enable_if_c<                    \
     unit_test::is_forward_iterable<Lhs>::value                      \
-    &&   !unit_test::is_cstring_comparable<Lhs>::value                         \
     && unit_test::is_forward_iterable<Rhs>::value                   \
-    &&   !unit_test::is_cstring_comparable<Rhs>::value>::type> {               \
+    && !(unit_test::is_cstring_comparable<Lhs>::value               \
+         && unit_test::is_cstring_comparable<Rhs>::value)>::type> { \
 public:                                                             \
     typedef assertion_result result_type;                           \
     typedef unit_test::bt_iterator_traits<Lhs> t_Lhs_iterator_helper; \

test/writing-test-ts/collection-comparison-test.cpp

@@ -142,6 +142,16 @@ BOOST_AUTO_TEST_CASE( test_collection_of_collection_comp )
 
 //____________________________________________________________________________//
 
+BOOST_AUTO_TEST_CASE( test_per_element_string_non_string )
+{
+    std::string a("abc");
+    std::vector<char> b{'a', 'b', 'c'};
+    BOOST_TEST( a == b, tt::per_element() );
+    BOOST_TEST( b == a, tt::per_element() );
+}
+
+//____________________________________________________________________________//
+
 // this one does not have const_iterator nor a size, but should be forward iterable
 // and possible to use in the collection comparison
 struct fwd_iterable_custom {