From d5948187018cdb447c3280c6d7c0878a406cfc76 Mon Sep 17 00:00:00 2001
From: overlookmotel <557937+overlookmotel@users.noreply.github.com>
Date: Tue, 3 Sep 2024 00:57:12 +0000
Subject: [PATCH] fix(traverse): `insert_scope_below` update child scopes
 records (#5409)

Follow on after #5403. Make `Traverse` update child scope IDs when inserting new scope. These lines were removed in #5232, but not reinstated in #5403.
---
 crates/oxc_semantic/src/scope.rs           | 13 +++++++++++++
 crates/oxc_traverse/src/context/scoping.rs |  6 ++++++
 2 files changed, 19 insertions(+)

diff --git a/crates/oxc_semantic/src/scope.rs b/crates/oxc_semantic/src/scope.rs
index 56498c12f3290..be50b57fba912 100644
--- a/crates/oxc_semantic/src/scope.rs
+++ b/crates/oxc_semantic/src/scope.rs
@@ -165,6 +165,7 @@ impl ScopeTree {
     pub fn set_parent_id(&mut self, scope_id: ScopeId, parent_id: Option<ScopeId>) {
         self.parent_ids[scope_id] = parent_id;
         if self.build_child_ids {
+            // Set this scope as child of parent scope
             if let Some(parent_id) = parent_id {
                 self.child_ids[parent_id].push(scope_id);
             }
@@ -247,12 +248,24 @@ impl ScopeTree {
         &mut self.bindings[scope_id]
     }
 
+    /// Return whether this `ScopeTree` has child IDs recorded
+    #[inline]
+    pub fn has_child_ids(&self) -> bool {
+        self.build_child_ids
+    }
+
     /// Get the child scopes of a scope
     #[inline]
     pub fn get_child_ids(&self, scope_id: ScopeId) -> &[ScopeId] {
         &self.child_ids[scope_id]
     }
 
+    /// Get a mutable reference to a scope's children
+    #[inline]
+    pub fn get_child_ids_mut(&mut self, scope_id: ScopeId) -> &mut Vec<ScopeId> {
+        &mut self.child_ids[scope_id]
+    }
+
     /// Create a scope.
     #[inline]
     pub fn add_scope(
diff --git a/crates/oxc_traverse/src/context/scoping.rs b/crates/oxc_traverse/src/context/scoping.rs
index 05f54633b4cf8..2ad9c60b26800 100644
--- a/crates/oxc_traverse/src/context/scoping.rs
+++ b/crates/oxc_traverse/src/context/scoping.rs
@@ -119,6 +119,12 @@ impl TraverseScoping {
     }
 
     fn insert_scope_below(&mut self, child_scope_ids: &[ScopeId], flags: ScopeFlags) -> ScopeId {
+        // Remove these scopes from parent's children
+        if self.scopes.has_child_ids() {
+            let current_child_scope_ids = self.scopes.get_child_ids_mut(self.current_scope_id);
+            current_child_scope_ids.retain(|scope_id| !child_scope_ids.contains(scope_id));
+        }
+
         // Create new scope as child of parent
         let new_scope_id = self.create_child_scope_of_current(flags);