Generate wildcard type parameters (#200)

* Generate wildcard type parameters

* add changelog item

Author: janmasrovira

effectful-th/CHANGELOG.md

@@ -1,5 +1,6 @@
 # effectful-th-1.0.0.2 (2024-??-??)
 * Drop support for GHC 8.8.
+* `makeEffect` no longer generates `Wunused-type-patterns` warning ([#200](https://github.com/haskell-effectful/effectful/pull/200)).
 
 # effectful-th-1.0.0.1 (2023-01-13)
 * Depend on `effectful-core`, not `effectful`.

effectful-th/src/Effectful/TH.hs

@@ -76,7 +76,7 @@ makeEffectImpl makeSig effName = do
   checkRequiredExtensions
   info <- reifyDatatype effName
   dispatch <- do
-    e <- getEff (ConT $ datatypeName info) (datatypeInstTypes info)
+    e <- getEff (ConT $ datatypeName info) (const WildCardT <$> datatypeInstTypes info)
     let dispatchE = ConT ''DispatchOf `AppT` e
         dynamic   = PromotedT 'Dynamic
     pure . TySynInstD $ TySynEqn Nothing dispatchE dynamic