Correlated sub-pipeline analysis is incorrect for $unionWith, leading to incorrect results

The following script reproduces the bug: (function() { "use strict";   const localColl = db.local_coll; localColl.drop();   assert.commandWorked(localColl.insert({a: "notMagic"})); assert.commandWorked(localColl.insert({a: "magicConstant"}));   const firstUnionColl = db.first_union_coll; firstUnionColl.drop(); assert.commandWorked(firstUnionColl.insert({unionedData: 1}));   const secondUnionColl = db.second_union_coll; secondUnionColl.drop(); assert.commandWorked(secondUnionColl.insert({unionedData: 2}));   let results = localColl.aggregate([ {$lookup: { from: firstUnionColl.getName(), as: "as", let: {correlatedVar: "$a"}, pipeline: [ {$_internalInhibitOptimization: {}}, {$unionWith: { coll: secondUnionColl.getName(), pipeline: [ {$match: {$expr: {$eq: ["$$correlatedVar", "magicConstant"]}}} ] }} ] }} ]).toArray();   printjson(results); }());