Preparse functions in the scope that was created when parsing of the function was started

src/ast/scopes.h

Index: src/ast/scopes.h
diff --git a/src/ast/scopes.h b/src/ast/scopes.h
index c5fcd6e7d2324f2ddab8225262d0f569c3458820..840c63944eb355ccfb5d4dbddee2c4a9128818f4 100644
--- a/src/ast/scopes.h
+++ b/src/ast/scopes.h
@@ -808,6 +808,20 @@ class DeclarationScope : public Scope {
   void AllocateParameterLocals();
   void AllocateReceiver();
 
+  void ResetAfterPreparsing() {
+    // Reset all non-trivial members.
+    decls_.Clear();
+    locals_.Clear();
+    params_.Clear();
+    sloppy_block_function_map_.Clear();
+    variables_.Clear();
+    // Make sure we won't walk the scope tree from here on.
+    inner_scope_ = nullptr;
+    // Make sure we won't try to allocate the rest parameter. {params_} was
+    // cleared above.
+    has_rest_ = false;
+  }
+
  private:
   void AllocateParameter(Variable* var, int index);