Add initial support for generators with parameters

rt/include/typon/generator.hpp

@@ -22,7 +22,7 @@ class Generator
 
     Promise() = default;
     std::suspend_always initial_suspend() { return {}; }
-    std::suspend_always final_suspend() noexcept { return {}; }
+    std::suspend_always final_suspend() noexcept { final = true; return {}; }
     void unhandled_exception() {
       std::rethrow_exception(std::move(std::current_exception()));
     }
@@ -47,11 +47,13 @@ class Generator
     }
 
     bool finished() {
-      return !value.has_value();
+      //return !value.has_value();
+      return final;
     }
 
   private:
     value_type value{};
+    bool final = false;
   };
 
 public:
@@ -68,7 +70,9 @@ public:
 
   Promise::value_type next() {
     if (handle) {
-      handle.resume();
+      if (!handle.promise().finished()) {
+        handle.resume();
+      }
       return handle.promise().get_value();
     }
     else {
@@ -135,7 +139,7 @@ public:
   }
 
   std::optional<value_type> py_next() {
-    return *begin();
+    return next();
   }
 
 private: