Added missing definitions of assignment operators.

This fixes incorrect return types of assignment operators imported from
base classes. Other than copy and move assignment operators, which are
generated by the compiler even if imported with a using-declaration,
the imported operators will be returning a reference to the base class
instead of the derived class.

In concurrent_queue, the assignment operator was missing while copy/move
constructors were present and contained non-trivial logic. The implicitly
generated assignment operator would have been incorrect. The added assignment
operator reuses copy/move constructors to implement assignment.

In concurrent_bounded_queue, the assignment operator was also missing and
would have been deleted because of std::atomic member, while the class also
had copy and move constructors. The added assignment operator also reuses
the existing constructors.

Fixes #312.
Fixes #372.
Fixes #373.

include/oneapi/tbb/concurrent_map.h

@@ -92,7 +92,6 @@ class concurrent_map : public concurrent_skip_list<map_traits<Key, Value, Compar
 
     // Include constructors of base type
     using base_type::base_type;
-    using base_type::operator=;
 
     // Required for implicit deduction guides
     concurrent_map() = default;
@@ -104,6 +103,11 @@ class concurrent_map : public concurrent_skip_list<map_traits<Key, Value, Compar
     concurrent_map& operator=( const concurrent_map& ) = default;
     concurrent_map& operator=( concurrent_map&& ) = default;
 
+    concurrent_map& operator=( std::initializer_list<value_type> il ) {
+        base_type::operator= (il);
+        return *this;
+    }
+
     // Observers
     mapped_type& at(const key_type& key) {
         iterator it = this->find(key);
@@ -239,7 +243,6 @@ class concurrent_multimap : public concurrent_skip_list<map_traits<Key, Value, C
     // Include constructors of base_type
     using base_type::base_type;
     using base_type::insert;
-    using base_type::operator=;
 
     // Required for implicit deduction guides
     concurrent_multimap() = default;
@@ -251,6 +254,11 @@ class concurrent_multimap : public concurrent_skip_list<map_traits<Key, Value, C
     concurrent_multimap& operator=( const concurrent_multimap& ) = default;
     concurrent_multimap& operator=( concurrent_multimap&& ) = default;
 
+    concurrent_multimap& operator=( std::initializer_list<value_type> il ) {
+        base_type::operator= (il);
+        return *this;
+    }
+
     template <typename P>
     typename std::enable_if<std::is_constructible<value_type, P&&>::value,
                             std::pair<iterator, bool>>::type insert( P&& value )

include/oneapi/tbb/concurrent_queue.h

@@ -114,6 +114,11 @@ class concurrent_queue {
         r1::cache_aligned_deallocate(my_queue_representation);
     }
 
+    concurrent_queue& operator= (concurrent_queue src) {
+        internal_swap(src);
+        return *this;
+    }
+
     // Enqueue an item at tail of queue.
     void push(const T& value) {
         internal_push(value);
@@ -344,6 +349,11 @@ class concurrent_bounded_queue {
                                          sizeof(queue_representation_type));
     }
 
+    concurrent_bounded_queue& operator= (concurrent_bounded_queue src) {
+        internal_swap(src);
+        return *this;
+    }
+
     // Enqueue an item at tail of queue.
     void push( const T& value ) {
         internal_push(value);

include/oneapi/tbb/concurrent_set.h

@@ -75,7 +75,6 @@ class concurrent_set : public concurrent_skip_list<set_traits<Key, Compare, conc
 
     // Include constructors of base_type
     using base_type::base_type;
-    using base_type::operator=;
 
     // Required for implicit deduction guides
     concurrent_set() = default;
@@ -87,6 +86,11 @@ class concurrent_set : public concurrent_skip_list<set_traits<Key, Compare, conc
     concurrent_set& operator=( const concurrent_set& ) = default;
     concurrent_set& operator=( concurrent_set&& ) = default;
 
+    concurrent_set& operator=( std::initializer_list<value_type> il ) {
+        base_type::operator= (il);
+        return *this;
+    }
+
     template<typename OtherCompare>
     void merge(concurrent_set<key_type, OtherCompare, Allocator>& source) {
         this->internal_merge(source);
@@ -172,7 +176,6 @@ class concurrent_multiset : public concurrent_skip_list<set_traits<Key, Compare,
 
     // Include constructors of base_type;
     using base_type::base_type;
-    using base_type::operator=;
 
     // Required for implicit deduction guides
     concurrent_multiset() = default;
@@ -184,6 +187,11 @@ class concurrent_multiset : public concurrent_skip_list<set_traits<Key, Compare,
     concurrent_multiset& operator=( const concurrent_multiset& ) = default;
     concurrent_multiset& operator=( concurrent_multiset&& ) = default;
 
+    concurrent_multiset& operator=( std::initializer_list<value_type> il ) {
+        base_type::operator= (il);
+        return *this;
+    }
+
     template<typename OtherCompare>
     void merge(concurrent_set<key_type, OtherCompare, Allocator>& source) {
         this->internal_merge(source);

include/oneapi/tbb/concurrent_unordered_map.h

@@ -70,7 +70,6 @@ class concurrent_unordered_map
 
     // Include constructors of base type
     using base_type::base_type;
-    using base_type::operator=;
 
     // Required for implicit deduction guides
     concurrent_unordered_map() = default;
@@ -82,6 +81,11 @@ class concurrent_unordered_map
     concurrent_unordered_map& operator=( const concurrent_unordered_map& ) = default;
     concurrent_unordered_map& operator=( concurrent_unordered_map&& ) = default;
 
+    concurrent_unordered_map& operator=( std::initializer_list<value_type> il ) {
+        base_type::operator= (il);
+        return *this;
+    }
+
     // Observers
     mapped_type& operator[]( const key_type& key ) {
         iterator where = this->find(key);
@@ -255,7 +259,6 @@ class concurrent_unordered_multimap
 
     // Include constructors of base type
     using base_type::base_type;
-    using base_type::operator=;
     using base_type::insert;
 
     // Required for implicit deduction guides
@@ -268,6 +271,11 @@ class concurrent_unordered_multimap
     concurrent_unordered_multimap& operator=( const concurrent_unordered_multimap& ) = default;
     concurrent_unordered_multimap& operator=( concurrent_unordered_multimap&& ) = default;
 
+    concurrent_unordered_multimap& operator=( std::initializer_list<value_type> il ) {
+        base_type::operator= (il);
+        return *this;
+    }
+
     template <typename P>
     typename std::enable_if<std::is_constructible<value_type, P&&>::value,
                             std::pair<iterator, bool>>::type insert( P&& value ) {

include/oneapi/tbb/concurrent_unordered_set.h

@@ -68,7 +68,7 @@ class concurrent_unordered_set
 
     // Include constructors of base_type;
     using base_type::base_type;
-    using base_type::operator=;
+
     // Required for implicit deduction guides
     concurrent_unordered_set() = default;
     concurrent_unordered_set( const concurrent_unordered_set& ) = default;
@@ -79,6 +79,11 @@ class concurrent_unordered_set
     concurrent_unordered_set& operator=( const concurrent_unordered_set& ) = default;
     concurrent_unordered_set& operator=( concurrent_unordered_set&& ) = default;
 
+    concurrent_unordered_set& operator=( std::initializer_list<value_type> il ) {
+        base_type::operator= (il);
+        return *this;
+    }
+
     template <typename OtherHash, typename OtherKeyEqual>
     void merge( concurrent_unordered_set<key_type, OtherHash, OtherKeyEqual, allocator_type>& source ) {
         this->internal_merge(source);
@@ -193,7 +198,6 @@ class concurrent_unordered_multiset
 
     // Include constructors of base_type;
     using base_type::base_type;
-    using base_type::operator=;
 
     // Required for implicit deduction guides
     concurrent_unordered_multiset() = default;
@@ -205,6 +209,11 @@ class concurrent_unordered_multiset
     concurrent_unordered_multiset& operator=( const concurrent_unordered_multiset& ) = default;
     concurrent_unordered_multiset& operator=( concurrent_unordered_multiset&& ) = default;
 
+    concurrent_unordered_multiset& operator=( std::initializer_list<value_type> il ) {
+        base_type::operator= (il);
+        return *this;
+    }
+
     template <typename OtherHash, typename OtherKeyEqual>
     void merge( concurrent_unordered_set<key_type, OtherHash, OtherKeyEqual, allocator_type>& source ) {
         this->internal_merge(source);