Adds a test case from #32

Author: konn

test/functional/Tactic.hs

@@ -94,6 +94,7 @@ tests = testGroup
   , goldenTest "GoldenNote.hs"              2 8  Auto ""
   , goldenTest "GoldenPureList.hs"          2 12 Auto ""
   , goldenTest "GoldenGADTDestruct.hs"      7 17 Destruct "gadt"
+  , goldenTest "GoldenGADTDestructCoercion.hs" 8 17 Destruct "gadt"
   , goldenTest "GoldenGADTAuto.hs"          7 13 Auto ""
   ]
 

test/testdata/tactic/GoldenGADTDestructCoercion.hs

@@ -0,0 +1,8 @@
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE GADTs #-}
+module GoldenGADTDestruct where
+data E a b where
+  E :: forall a b. (b ~ a, Ord a) => b -> E a [a]
+
+ctxGADT :: E a b -> String
+ctxGADT gadt = _decons

test/testdata/tactic/GoldenGADTDestructCoercion.hs.expected

@@ -0,0 +1,8 @@
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE GADTs #-}
+module GoldenGADTDestruct where
+data E a b where
+  E :: forall a b. (b ~ a, Ord a) => b -> E a [a]
+
+ctxGADT :: E a b -> String
+ctxGADT gadt = (case gadt of { (E b) -> _ })