Test Trac #3176

testsuite/tests/ghc-regress/typecheck/should_fail/T3176.hs

+{-# LANGUAGE ExistentialQuantification #-}
+
+-- Trac #3176
+
+module Foo where
+
+data ES = forall a. Show a => ES {unES:: a}
+
+smallPrintES f t = show $ unES $ f t 

testsuite/tests/ghc-regress/typecheck/should_fail/T3176.stderr

+
+T3176.hs:9:26:
+    Cannot use record selector `unES' as a function due to escaped type variables
+    Probable fix: use pattern-matching syntax instead
+    In the first argument of `($)', namely `unES'
+    In the second argument of `($)', namely `unES $ f t'
+    In the expression: show $ unES $ f t

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

@@ -208,3 +208,4 @@ test('T2688', normal, compile_fail, [''])
 test('T2714', normal, compile_fail, [''])
 test('T2994', normal, compile_fail, [''])
 test('T3155', normal, compile_fail, [''])
+test('T3176', normal, compile_fail, [''])