Add pointer_like<X> as X cast

Author: filipsajdak

include/cpp2util.h

@@ -1352,6 +1352,18 @@ auto as( X* x ) -> C {
     return Dynamic_cast<C>(x);
 }
 
+template <pointer_like T>
+using pointee_t = CPP2_TYPEOF(*std::declval<T>());
+
+template < typename C, pointer_like X>
+    requires std::same_as<pointee_t<X>, C>
+auto as (X const & x) -> decltype(auto) {
+    if (x) {
+        return *x;
+    }
+    Throw( std::runtime_error("'as' cast failed for empty 'pointer_like'"), "'as' cast failed for empty 'pointer_like'");
+}
+
 //-------------------------------------------------------------------------------------------------------------
 //  std::variant is and as
 //