Move return type to param_names.

src/plugin.rs

@@ -30,12 +30,9 @@ pub trait PluginFunction {
     /// Convert a plugin function into a boxed trait object.
     fn clone_boxed(&self) -> Box<dyn PluginFunction>;
 
-    /// Return a boxed slice of the names of the function's parameters.
-    fn input_names(&self) -> Box<[&'static str]>;
+    /// Return a boxed slice of the names of the function's parameters and return type.
+    fn param_names(&self) -> Box<[&'static str]>;
 
     /// Return a boxed slice of type ID's of the function's parameters.
     fn input_types(&self) -> Box<[TypeId]>;
-
-    /// Return a string slice of the function's return type.
-    fn return_type(&self) -> &'static str;
 }