New returns optional of owning reference

include/cpp2util.h

@@ -711,8 +711,28 @@ struct {
 } inline shared;
 
 template<typename T>
-[[nodiscard]] auto cpp2_new(auto&& ...args) -> std::unique_ptr<T> {
-    return unique.cpp2_new<T>(CPP2_FORWARD(args)...);
+class owning_reference {
+public:
+    explicit owning_reference(std::unique_ptr<T>&& ptr):_ptr(cpp2::impl::assert_not_null(std::move(ptr))){}
+    ~owning_reference() = default;
+    owning_reference(const owning_reference& ref) = delete;
+    owning_reference& operator=(const owning_reference& ref) noexcept = delete;
+    owning_reference(owning_reference&& ref) = default;
+    owning_reference& operator=(owning_reference&& ref) noexcept = default;
+    typename std::add_lvalue_reference<T>::type operator*() const { return *cpp2::impl::assert_not_null(_ptr.get()); }
+    typename std::add_lvalue_reference<T>::type operator->() const noexcept {return *cpp2::impl::assert_not_null(_ptr.get());}
+    auto get() const noexcept { return _ptr.get();}
+private:
+   std::unique_ptr<T> _ptr; 
+};
+
+template<typename T>
+[[nodiscard]] auto cpp2_new(auto&& ...args) -> std::optional<owning_reference<T>> {
+    auto _ptr = unique.cpp2_new<T>(CPP2_FORWARD(args)...);
+    if (_ptr) {
+        return owning_reference<T>{std::move(_ptr)};
+    }
+    return {};
 }
 
 

regression-tests/mixed-type-safety-1.cpp2

@@ -29,7 +29,7 @@ main: () -> int =
     print( "1   is int? ", 1   is int );
 
     c := new<Circle>();     // safe by construction
-    s : * Shape = c.get();  // safe by Lifetime
+    s : * Shape = c*.get();  // safe by Lifetime
     print("\ns* is Shape?  ", s* is Shape  );
     print(  "s* is Circle? ", s* is Circle );
     print(  "s* is Square? ", s* is Square );

regression-tests/pure2-intro-example-three-loops.cpp2

@@ -12,7 +12,12 @@ main: () -> int = {
         ( "hello", "big", "world" );
     view: std::span<std::string> = words;
 
-    i := new<int>(0);
+    p_i := new<int>(0);
+    if (!p_i) {
+        return 1;
+    }
+    i := (move p_i*);
+
     while i* < view.ssize() next i*++ {
         print( view[i*] );
     }