Test for Trac #2478

testsuite/tests/ghc-regress/typecheck/should_compile/T2478.hs

+{-# OPTIONS -fglasgow-exts #-}
+
+module ShouldCompile where
+
+  data Eq t => TrafoE t = forall env2 . TrafoE Int t
+
+  newSRef () = TrafoE 

testsuite/tests/ghc-regress/typecheck/should_compile/all.T

@@ -272,6 +272,7 @@ test('FD4', normal, compile, [''])
 test('faxen', normal, compile, [''])
 test('T1495', normal, compile, [''])
 test('T2045', normal, compile, [''])   # Needs -fhpc
+test('T2478', normal, compile, ['']) 
 
 # Omitting temporarily
 test('syn-perf', normal, compile, ['-fcontext-stack=30'])