setup-dotnet/.github/csc.json

{
    "problemMatcher": [
        {
            "owner": "csc",
            "pattern": [
                {
                    "regexp": "^([^\\s].*)\\((\\d+|\\d+,\\d+|\\d+,\\d+,\\d+,\\d+)\\):\\s+(error|warning|info)\\s+(CS\\d+)\\s*:\\s*(.*)$",
                    "file": 1,
                    "location": 2,
                    "severity": 3,
                    "code": 4,
                    "message": 5
                }
            ]
        }
    ]
}