Use recursive mapped type

types/deep-freeze/deep-freeze-tests.ts

@@ -3,5 +3,5 @@ import df = require('deep-freeze');
 class Foo {
     foo: string;
 }
-const foo: Foo = df(new Foo());
+const foo = df(new Foo());
 const items = [{id: 0, name: 'first'}];

types/deep-freeze/index.d.ts

@@ -10,4 +10,4 @@ declare function deepFreeze<T>(a: T[]): ReadonlyArray<DeepReadonly<T>>;
 declare function deepFreeze<T extends Function>(f: T): T;
 declare function deepFreeze<T>(o: T): DeepReadonly<T>;
 
-type DeepReadonly<T> = Readonly<{ [P in keyof T]: Readonly<T[P]> }>;
+type DeepReadonly<T> = Readonly<{ [P in keyof T]: DeepReadonly<T[P]> }>;