VARIATION ParentOverwritesEmbeddedScope
input: {
    "pipeline": [
        {
            "$set": {
                "a": {
                    "b": {
                        "$const": 1
                    },
                    "c": {
                        "$const": 2
                    }
                }
            }
        },
        {
            "$set": {
                "a": {
                    "$const": 3
                }
            }
        },
        {
            "$match": {
                "a.b": 1
            }
        }
    ]
}
output: {
    "$set:0": {
        "scope:0": {
            "exhaustiveScope": "scope:-1",
            "fields": {
                "<missing>:0": {
                    "declaringScope": "scope:0",
                    "dependencies": []
                },
                "a:1": {
                    "declaringScope": "scope:0",
                    "scope:1": {
                        "exhaustiveScope": "scope:-1",
                        "fields": {
                            "<missing>:2": {
                                "declaringScope": "scope:1",
                                "dependencies": []
                            },
                            "b:3": {
                                "declaringScope": "scope:1",
                                "dependencies": []
                            },
                            "c:4": {
                                "declaringScope": "scope:1",
                                "dependencies": []
                            }
                        }
                    },
                    "dependencies": [
                        "b:3",
                        "c:4"
                    ]
                }
            }
        },
        "dependencies": []
    },
    "$set:1": {
        "scope:2": {
            "exhaustiveScope": "scope:-1",
            "fields": {
                "<missing>:5": {
                    "declaringScope": "scope:2",
                    "dependencies": []
                },
                "a:6": {
                    "declaringScope": "scope:2",
                    "dependencies": []
                }
            }
        },
        "dependencies": []
    },
    "$match:2": {
        "scope:2": "scope:2",
        "dependencies": []
    }
}

