<!-- This template is for bugs relating to Ember.js type information. Please fill out all of the required information below --> ### Which package(s) does this problem pertain to? - [x] @types/ember - [x] @types/ember-data ### What are instructions we can follow to reproduce the issue? ```sh npm install -g typescript@latest tsc -v # make sure it's a v3.x (i.e. Version 3.1.0-dev.20180810) git clone https://github.com/DefinitelyTyped/DefinitelyTyped cd DefinitelyTyped npm install cd types/ember tsc ``` <!-- example: "Create a new route, add an action to it as shown in the following code sample" --> ### Now about that bug. What did you expect to see? I expected `tsc` to compile the ambient types and test files successfully ### What happened instead? ```ts test/array-ext.ts:16:32 - error TS2345: Argument of type 'ComputedProperty<Fix<Person & { name: string; }> | undefined, Fix<Person & { name: string; }> | undefined>'is not assignable to parameter of type 'Person'. Property 'name' is missing in type 'ComputedProperty<Fix<Person & { name: string; }> | undefined, Fix<Person & { name: string; }> | undefined>'. 16 assertType<Person | undefined>(array.get('firstObject')); ``` ### NOTE Switching to a TypeScript 2.x ``` npm install -g typescript@2 tsc ``` will compile the tests successfully and without error.