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

ast/src/ast_gen.rs

@@ -24,6 +24,24 @@ impl<T> Located<T> {
             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
+    }
 }
 
 #[derive(Clone, Debug, PartialEq)]