# old/mod.ts
class Base {}
export class Foo extends Base {}

# new/mod.ts
class Other {}
export class Foo extends Other {}

# output.json
{
  "modifiedModules": {
    "file:///mod.ts": {
      "modified": [
        {
          "name": "Other",
          "nameChange": {
            "old": "Base",
            "new": "Other"
          }
        },
        {
          "name": "Foo",
          "declarations": {
            "modified": [
              {
                "kind": "class",
                "defChanges": {
                  "type": "class",
                  "extendsChange": {
                    "old": "Base",
                    "new": "Other"
                  }
                }
              }
            ]
          }
        }
      ]
    }
  }
}
