Per the [JSDuck documentation](https://github.com/senchalabs/jsduck/wiki/Type-Definitions#type-names), values can be literals of booleans, numbers or strings. However, only the first of these works. ### Literals which work - `{true}` - `{false}` - `{true|false}` ### Literals which fail - `{'foo'}` - `{"bar"}` - `{'foo'|"bar"}` - `{42}` - `{42|24}`