Add operator= for direct assignment to defaulted value

Author: polytypic

provides/include/dumpster_v1/defaulted.hpp

@@ -21,3 +21,10 @@ template <class Value, auto... defaults>
 dumpster_v1::defaulted<Value, defaults...>::operator Value &() {
   return value;
 }
+
+template <class Value, auto... defaults>
+template <class Forwardable>
+Value &dumpster_v1::defaulted<Value, defaults...>::
+operator=(Forwardable &&rhs) {
+  return value = rhs;
+}

provides/include/dumpster_v1/synopsis.hpp

@@ -23,6 +23,9 @@ template <class Value, auto... defaults> struct defaulted {
   /// Implicit conversion to reference for convenience.
   operator Value &();
 
+  /// Assigns given `rhs` to `value` member.
+  template <class Forwardable> Value &operator=(Forwardable &&rhs);
+
   /// The value is directly accessible as there is no reason to hide it.
   Value value;
 };