# old/mod.ts
export function foo(): string { return ""; }

# new/mod.ts
export function foo(): number { return 0; }

# output.json
{
  "modifiedModules": {
    "file:///mod.ts": {
      "modified": [
        {
          "name": "foo",
          "declarations": {
            "modified": [
              {
                "kind": "function",
                "defChanges": {
                  "type": "function",
                  "returnTypeChange": {
                    "old": {
                      "repr": "string",
                      "kind": "keyword",
                      "value": "string"
                    },
                    "new": {
                      "repr": "number",
                      "kind": "keyword",
                      "value": "number"
                    }
                  }
                }
              }
            ]
          }
        }
      ]
    }
  }
}
