Haskell Language Type Families Injectivity
Example
Type Families are not necessarily injective. Therefore, we cannot infer the parameter from an application. For example, in servant, given a type Server a we cannot infer the type a. To solve this problem, we can use Proxy. For example, in servant, the serve function has type ... Proxy a -> Server a -> .... We can infer a from Proxy a because Proxy is defined by data which is injective.
