Imagine the following file:

// comment

function f() {}

When I press Ctrl+x on the line containing f , and paste it again, what VS Code does is it creates a buffer with the following contents:

// comment

and then sends this request for paste edits

{
    "file": "d:\\scratch\\copypasta\\src\\file.ts",
    "pastedText": [
        "function f() {}\r\n"
    ],
    "pasteLocations": [
        {
            "start": {
                "line": 2,
                "offset": 1
            },
            "end": {
                "line": 2,
                "offset": 1
            }
        }
    ],
    "copiedFrom": {
        "file": "d:\\scratch\\copypasta\\src\\file.ts",
        "spans": [
            {
                "start": {
                    "line": 3,
                    "offset": 1
                },
                "end": {
                    "line": 3,
                    "offset": 16
                }
            }
        ]
    }
}

and receives this response.

{
    "edits": [
        {
            "fileName": "d:/scratch/copypasta/src/file.ts",
            "textChanges": [
                {
                    "start": {
                        "line": 1,
                        "offset": 15
                    },
                    "end": {
                        "line": 1,
                        "offset": 15
                    },
                    "newText": "function f() {}\r\n"
                }
            ]
        }
    ],
    "fixId": "providePostPasteEdits"
}

After the paste, the file no longer contains the original contents, and instead contains invalid text.

// commentfunction f() {}