# old/mod.ts
interface Base { id: number; }
export interface Foo {
  name: string;
}

# new/mod.ts
interface Base { id: number; }
export interface Foo extends Base {
  name: string;
}

# output.json
{
  "modifiedModules": {
    "file:///mod.ts": {
      "added": [
        {
          "name": "Base",
          "declarations": [
            {
              "location": {
                "filename": "file:///mod.ts",
                "line": 0,
                "col": 0,
                "byteIndex": 0
              },
              "declarationKind": "private",
              "kind": "interface",
              "def": {
                "properties": [
                  {
                    "name": "id",
                    "location": {
                      "filename": "file:///mod.ts",
                      "line": 0,
                      "col": 17,
                      "byteIndex": 17
                    },
                    "tsType": {
                      "repr": "number",
                      "kind": "keyword",
                      "value": "number"
                    }
                  }
                ]
              }
            }
          ]
        }
      ],
      "modified": [
        {
          "name": "Foo",
          "declarations": {
            "modified": [
              {
                "kind": "interface",
                "defChanges": {
                  "type": "interface",
                  "extendsChange": {
                    "added": [
                      {
                        "repr": "Base",
                        "kind": "typeRef",
                        "value": {
                          "typeName": "Base",
                          "resolution": {
                            "kind": "local"
                          }
                        }
                      }
                    ]
                  }
                }
              }
            ]
          }
        }
      ]
    }
  }
}
