Use options struct for function type factory function.

libsolidity/ast/Types.h

@@ -1247,6 +1247,38 @@ public:
 		/// Cannot be called.
 		Declaration,
 	};
+	struct Options
+	{
+		/// true iff the function takes an arbitrary number of arguments of arbitrary types
+		bool arbitraryParameters = false;
+		/// true iff the gas value to be used is on the stack
+		bool gasSet = false;
+		/// true iff the value to be sent is on the stack
+		bool valueSet = false;
+		/// iff the salt value (for create2) to be used is on the stack
+		bool saltSet = false;
+		/// true iff the function is called as arg1.fun(arg2, ..., argn).
+		/// This is achieved through the "using for" directive.
+		bool bound = false;
+
+		static Options withArbitraryParameters()
+		{
+			Options result;
+			result.arbitraryParameters = true;
+			return result;
+		}
+		static Options fromFunctionType(FunctionType const& _type)
+		{
+			Options result;
+			result.arbitraryParameters = _type.takesArbitraryParameters();
+			result.gasSet = _type.gasSet();
+			result.valueSet = _type.valueSet();
+			result.saltSet = _type.saltSet();
+			result.bound = _type.bound();
+			return result;
+		}
+	};
+
 
 	/// Creates the type of a function.
 	/// @arg _kind must be Kind::Internal, Kind::External or Kind::Declaration.