meteficha/hissmetrics — pull request #1 by alanpog (2012-05-15 02:31:18+00:00)
Title: Adding type flexibility and convenience to CallType

This commit addresses two issues with `CallType`: 1)it's type had only one Identity type variable, which forced the `Alias` constructor parameters to agree in types, 2) Some constructors don't specify all type variables (for example `Alias` doesn't specify an `event`), so we got an ambiguity error from the compiler when using those constructors, unless we added an explicit type annotation, which was annoying.
The first issued was resolved by simply adding a second `Identity` type variable. For the second issue I made `CallType` a GADT (which means we lost all automatically derived instances for `CallType`. Do you know of an easier fix?).