Add test for regression of mkYesod

yesod-core/test/YesodCoreTest/ParameterizedSite.hs

@@ -11,12 +11,14 @@ import Yesod.Core.Dispatch (toWaiApp)
 
 import YesodCoreTest.ParameterizedSite.PolyAny (PolyAny (..))
 import YesodCoreTest.ParameterizedSite.PolyShow (PolyShow (..))
+import YesodCoreTest.ParameterizedSite.Compat (Compat (..))
 
 -- These are actually tests for template haskell. So if it compiles, it works
 parameterizedSiteTest :: Spec
 parameterizedSiteTest = describe "Polymorphic Yesod sites" $ do
     it "Polymorphic unconstrained stub" $ runStub (PolyAny ())
     it "Polymorphic stub with Show" $ runStub' "1337" (PolyShow 1337)
+    it "Polymorphic unconstrained stub, old-style" $ runStub (Compat () ())
 
 runStub :: YesodDispatch a => a -> IO ()
 runStub stub =

yesod-core/test/YesodCoreTest/ParameterizedSite/Compat.hs

@@ -0,0 +1,27 @@
+{-# LANGUAGE
+    TypeFamilies, QuasiQuotes, TemplateHaskell, MultiParamTypeClasses
+  , OverloadedStrings, StandaloneDeriving, FlexibleInstances
+  #-}
+module YesodCoreTest.ParameterizedSite.Compat
+    ( Compat (..)
+    ) where
+
+import Yesod.Core
+
+-- | Parameterized without constraints, and we call mkYesod without type vars,
+-- like people used to do before the last 3 commits
+data Compat a b = Compat a b
+
+mkYesod "Compat" [parseRoutes|
+/ HomeR GET
+|]
+
+instance Yesod (Compat a b)
+
+getHomeR :: Handler a b Html
+getHomeR = defaultLayout
+    [whamlet|
+        <p>
+            Stub
+    |]
+

yesod-core/yesod-core.cabal

@@ -157,6 +157,7 @@ test-suite tests
                    YesodCoreTest.NoOverloadedStrings
                    YesodCoreTest.NoOverloadedStringsSub
                    YesodCoreTest.ParameterizedSite
+                   YesodCoreTest.ParameterizedSite.Compat
                    YesodCoreTest.ParameterizedSite.PolyAny
                    YesodCoreTest.ParameterizedSite.PolyShow
                    YesodCoreTest.RawResponse