load('jstests/aggregation/extras/utils.js');

db.server5782.drop();
db.server5782.save({string: "foo"});

// check that without $literal we end up comparing a field with itself and the result is true
var result = db.runCommand({aggregate: "server5782",
                            pipeline:[{$project:
                                {stringis$string: {$eq:["$string", '$string']}}
             }]});
assert.eq(result.result[0].stringis$string, true);

// check that with $literal we end up comparing a field with '$string' and the result is true
var result = db.runCommand({aggregate: "server5782",
                            pipeline:[{$project:
                                {stringis$string: {$eq:["$string", {$literal:'$string'}]}}
             }]});
assert.eq(result.result[0].stringis$string, false);