fix: Map new replacement nodes to their mutable equivalents in SyntaxEditor

Author: Giga-Bowser

crates/ide-assists/src/handlers/reorder_fields.rs

@@ -93,8 +93,7 @@ fn replace<T: AstNode + PartialEq>(
     sorted_fields: impl IntoIterator<Item = T>,
 ) {
     fields.zip(sorted_fields).for_each(|(field, sorted_field)| {
-        // FIXME: remove `clone_for_update` when `SyntaxEditor` handles it for us
-        editor.replace(field.syntax(), sorted_field.syntax().clone_for_update())
+        editor.replace(field.syntax(), sorted_field.syntax())
     });
 }
 

crates/syntax/src/syntax_editor/edit_algo.rs

@@ -154,6 +154,12 @@ pub(super) fn apply_edits(editor: SyntaxEditor) -> SyntaxEdit {
                     }
                 };
             }
+            Change::Replace(SyntaxElement::Node(target), Some(SyntaxElement::Node(new_target))) => {
+                *target = tree_mutator.make_syntax_mut(target);
+                if new_target.ancestors().any(|node| node == tree_mutator.immutable) {
+                    *new_target = new_target.clone_for_update();
+                }
+            }
             Change::Replace(target, _) | Change::ReplaceWithMany(target, _) => {
                 *target = tree_mutator.make_element_mut(target);
             }