{
    "message": "unused variable: `foo`",
    "code": {
        "code": "unused_variables",
        "explanation": null
    },
    "level": "warning",
    "spans": [
        {
            "file_name": "driver/subcommand/repl.rs",
            "byte_start": 9228,
            "byte_end": 9231,
            "line_start": 291,
            "line_end": 291,
            "column_start": 9,
            "column_end": 12,
            "is_primary": true,
            "text": [
                {
                    "text": "    let foo = 42;",
                    "highlight_start": 9,
                    "highlight_end": 12
                }
            ],
            "label": null,
            "suggested_replacement": null,
            "suggestion_applicability": null,
            "expansion": null
        }
    ],
    "children": [
        {
            "message": "#[warn(unused_variables)] on by default",
            "code": null,
            "level": "note",
            "spans": [],
            "children": [],
            "rendered": null
        },
        {
            "message": "consider prefixing with an underscore",
            "code": null,
            "level": "help",
            "spans": [
                {
                    "file_name": "driver/subcommand/repl.rs",
                    "byte_start": 9228,
                    "byte_end": 9231,
                    "line_start": 291,
                    "line_end": 291,
                    "column_start": 9,
                    "column_end": 12,
                    "is_primary": true,
                    "text": [
                        {
                            "text": "    let foo = 42;",
                            "highlight_start": 9,
                            "highlight_end": 12
                        }
                    ],
                    "label": null,
                    "suggested_replacement": "_foo",
                    "suggestion_applicability": "MachineApplicable",
                    "expansion": null
                }
            ],
            "children": [],
            "rendered": null
        }
    ],
    "rendered": "warning: unused variable: `foo`\n   --> driver/subcommand/repl.rs:291:9\n    |\n291 |     let foo = 42;\n    |         ^^^ help: consider prefixing with an underscore: `_foo`\n    |\n    = note: #[warn(unused_variables)] on by default\n\n"
}