I am attempting to use `async/await` in an angular `1.5.5` project.

Given this service method

```
    getDocumentTypes(): angular.IPromise<DocumentType[]> {
        var url = "api/document/types";
        this.$log.log(url);
        return this.$http.get(url).then(_ => _.data);
    }

```

I am attempting to create an `async / await` version of the method. 

```
    async getDocTypes(): angular.IPromise<DocumentType[]> {
                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    }}

```

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> > Intellisense shows an error: `TS1055` Type **'angular.IPromise'** is not a valid async function return type in `ES5/ES3` because it does not refer to a **Promise-compatible** constructor value.
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Is there a correct way to use an **angular promise** in *typescript 2.1* with `async` / `await`?