Improve tests for vector and deque move-assignment

	* testsuite/23_containers/deque/allocator/move_assign-2.cc: Improve
	comment. Ensure first test works because allocator type propagates and
	not because is_always_equal is true.
	* testsuite/23_containers/vector/52591.cc: Likewise. Restore original
	testcase that instantiates the move-assignment operator.

From-SVN: r247284

libstdc++-v3/ChangeLog

+2017-04-26  Jonathan Wakely  <jwakely@redhat.com>
+
+	* testsuite/23_containers/deque/allocator/move_assign-2.cc: Improve
+	comment. Ensure first test works because allocator type propagates and
+	not because is_always_equal is true.
+	* testsuite/23_containers/vector/52591.cc: Likewise. Restore original
+	testcase that instantiates the move-assignment operator.
+
 2017-04-24  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/80506

libstdc++-v3/testsuite/23_containers/deque/allocator/move_assign-2.cc

@@ -25,9 +25,9 @@
 #include <type_traits>
 
 
-// As an extension we allow move-assignment of std::deque when the element
-// type is not MoveAssignable, as long as the allocator type propagates or
-// is known to always compare equal.
+// Move-assignment of std::deque<T> is allowed for non-MoveAssignable T when
+// the allocator type propagates. As an extension we also allow it if the
+// allocator type is known to always compare equal.
 
 struct C
 {
@@ -43,6 +43,7 @@ struct A1 : std::allocator<T>
   template<typename U> A1(const A1<U>&) { }
 
   using propagate_on_container_move_assignment = std::true_type;
+  using is_always_equal = std::false_type;
 };
 
 void test01()

libstdc++-v3/testsuite/23_containers/vector/52591.cc

@@ -23,15 +23,21 @@
 #include <memory>
 #include <type_traits>
 
-// As an extension we allow move-assignment of std::vector when the element
-// type is not MoveAssignable, as long as the allocator type propagates or
-// is known to always compare equal.
+// Move-assignment of std::vector<T> is allowed for non-MoveAssignable T when
+// the allocator type propagates. As an extension we also allow it if the
+// allocator type is known to always compare equal.
 
 struct C
 {
     C& operator=(C&&) = delete;
 };
 
+void test01()
+{
+    std::vector<C> a;
+    a = std::vector<C>();
+}
+
 template<typename T>
 struct A1 : std::allocator<T>
 {
@@ -41,9 +47,10 @@ struct A1 : std::allocator<T>
   template<typename U> A1(const A1<U>&) { }
 
   using propagate_on_container_move_assignment = std::true_type;
+  using is_always_equal = std::false_type;
 };
 
-void test01()
+void test02()
 {
   using test_type = std::vector<C, A1<C>>;
   static_assert(std::is_nothrow_move_assignable<test_type>::value,
@@ -62,7 +69,7 @@ struct A2 : std::allocator<T>
   using is_always_equal = std::true_type;
 };
 
-void test02()
+void test03()
 {
   using test_type = std::vector<C, A2<C>>;
   static_assert(std::is_nothrow_move_assignable<test_type>::value,