Add Located::start, Located::end and impl Deref

ast/asdl_rs.py

@@ -671,6 +671,24 @@ def write_ast_def(mod, typeinfo, f):
             pub fn new(location: Location, end_location: Location, node: T) -> Self {
                 Self { location, end_location: Some(end_location), custom: (), node }
             }
+            
+            pub const fn start(&self) -> Location {
+                self.location
+            }
+            
+            /// Returns the node's [`end_location`](Located::end_location) or [`location`](Located::start) if 
+            /// [`end_location`](Located::end_location) is `None`.
+            pub fn end(&self) -> Location {
+                self.end_location.unwrap_or(self.location)
+            }      
+        }
+        
+        impl<T, U> std::ops::Deref for Located<T, U> {
+            type Target = T;
+            
+            fn deref(&self) -> &Self::Target {
+                &self.node
+            }
         }
         \n
     """.lstrip()