add value-initialization

Author: m-fila

doc/collections_as_container.md

@@ -83,7 +83,7 @@ In the following tables a convention from `Collection` is used: `iterator` stand
 | `std::indirectly_readable` | ❌ no | ❌ no |
 | `std::indirectly_writable` | ❌ no | ❌ no |
 | `std::weakly_incrementable` | ✔️ yes | ✔️ yes |
-| `std::incrementable` | ❌ no | ❌ no |
+| `std::incrementable` | ✔️ yes | ✔️ yes |
 | `std::input_or_output_iterator` | ✔️ yes | ✔️ yes |
 | `std::input_iterator` | ❌ no | ❌ no |
 | `std::output_iterator` | ❌ no | ❌ no |
@@ -134,10 +134,10 @@ In addition to the *LegacyForwardIterator* the C++ standard specifies also the *
 | Requirement | Fulfilled by `iterator`/`const_iterator`? | Comment |
 |-------------|-------------------------------------------|---------|
 | [*LegacyInputIterator*](https://en.cppreference.com/w/cpp/named_req/InputIterator) | ✔️ yes / ✔️ yes | [See above](#legacyinputiterator)|
-| [*DefaultConstructible*](https://en.cppreference.com/w/cpp/named_req/DefaultConstructible) | ❌ no / ❌ no | Value initialization not defined |
+| [*DefaultConstructible*](https://en.cppreference.com/w/cpp/named_req/DefaultConstructible) | ✔️ yes / ✔️ yes | |
 | If *mutable* iterator then `reference` same as `value_type&` or `value_type&&`, otherwise same as `const value_type&` or `const value_type&&` | ❌ no / ❌ no | `reference` type is not a reference (`&` or `&&`) |
 | [Multipass guarantee](https://en.cppreference.com/w/cpp/named_req/ForwardIterator) | ❌ no / ❌ no | References from dereferencing equal iterators aren't bound to the same object |
-| [Singular iterators](https://en.cppreference.com/w/cpp/named_req/ForwardIterator) | ❌ no / ❌ no | Value initialization not defined |
+| [Singular iterators](https://en.cppreference.com/w/cpp/named_req/ForwardIterator) | ✔️ yes / ✔️ yes | |
 
 | Expression | Return type | Semantics | Fulfilled by `iterator`/`const_iterator`? | Comment |
 |------------|-------------|-----------|-------------------------------------------|---------|

python/templates/macros/iterator.jinja2

@@ -10,6 +10,7 @@ public:
   using iterator_category = std::input_iterator_tag;
 
   {{ iterator_type }}(size_t index, const {{ class.bare_type }}ObjPointerContainer* collection) : m_index(index), m_object({{ ptr_init }}), m_collection(collection) {}
+  {{ iterator_type }}(): {{ iterator_type }}(0, nullptr) {}
 
   {{ iterator_type }}(const {{ iterator_type }}&) = default;
   {{ iterator_type }}({{ iterator_type }}&&) = default;

tests/unittests/std_interoperability.cpp

@@ -415,7 +415,7 @@ TEST_CASE("Collection and iterator concepts") {
     DOCUMENTED_STATIC_FAILURE(std::indirectly_readable<iterator>);
     DOCUMENTED_STATIC_FAILURE(std::indirectly_writable<iterator, CollectionType::value_type>);
     STATIC_REQUIRE(std::weakly_incrementable<iterator>);
-    DOCUMENTED_STATIC_FAILURE(std::incrementable<iterator>);
+    STATIC_REQUIRE(std::incrementable<iterator>);
     STATIC_REQUIRE(std::input_or_output_iterator<iterator>);
     DOCUMENTED_STATIC_FAILURE(std::input_iterator<iterator>);
     DOCUMENTED_STATIC_FAILURE(std::output_iterator<iterator, CollectionType::value_type>);
@@ -428,7 +428,7 @@ TEST_CASE("Collection and iterator concepts") {
     DOCUMENTED_STATIC_FAILURE(std::indirectly_readable<const_iterator>);
     DOCUMENTED_STATIC_FAILURE(std::indirectly_writable<const_iterator, CollectionType::value_type>);
     STATIC_REQUIRE(std::weakly_incrementable<const_iterator>);
-    DOCUMENTED_STATIC_FAILURE(std::incrementable<const_iterator>);
+    STATIC_REQUIRE(std::incrementable<const_iterator>);
     STATIC_REQUIRE(std::input_or_output_iterator<const_iterator>);
     DOCUMENTED_STATIC_FAILURE(std::input_iterator<const_iterator>);
     DOCUMENTED_STATIC_FAILURE(std::output_iterator<const_iterator, CollectionType::value_type>);
@@ -655,9 +655,9 @@ TEST_CASE("Collection iterators", "[collection][container][iterator][std]") {
 
     // DefaultConstructible
     // iterator
-    DOCUMENTED_STATIC_FAILURE(std::is_default_constructible_v<iterator>);
+    STATIC_REQUIRE(std::is_default_constructible_v<iterator>);
     // const_iterator
-    DOCUMENTED_STATIC_FAILURE(std::is_default_constructible_v<const_iterator>);
+    STATIC_REQUIRE(std::is_default_constructible_v<const_iterator>);
 
     // Multipass guarantee
     // iterator
@@ -704,16 +704,12 @@ TEST_CASE("Collection iterators", "[collection][container][iterator][std]") {
     // Singular iterators
     // iterator
     STATIC_REQUIRE(traits::has_equality_comparator_v<iterator>);
-    DOCUMENTED_STATIC_FAILURE(std::is_default_constructible_v<iterator>);
-    //{
-    //  REQUIRE(iterator{} == iterator{});
-    //}
+    STATIC_REQUIRE(std::is_default_constructible_v<iterator>);
+    { REQUIRE(iterator{} == iterator{}); }
     // const_iterator
     STATIC_REQUIRE(traits::has_equality_comparator_v<const_iterator>);
-    DOCUMENTED_STATIC_FAILURE(std::is_default_constructible_v<const_iterator>);
-    //{
-    //  REQUIRE(const_iterator{} == const_iterator{});
-    //}
+    STATIC_REQUIRE(std::is_default_constructible_v<const_iterator>);
+    { REQUIRE(const_iterator{} == const_iterator{}); }
 
     // i++
     // iterator