rs-cargo/dist/.matchers/rustfmt.json

{
    "problemMatcher": [
        {
            "owner": "rustfmt",
            "pattern": [
                {
                    "regexp": "^Diff in (\\S+) at line (\\d+):$",
                    "file": 1,
                    "line": 2
                }
            ]
        }
    ]
}