Also test the other part of #2806 in tcfail203

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

@@ -198,9 +198,7 @@ test('tcfail199', normal, compile_fail, [''])
 test('tcfail200', normal, compile_fail, [''])
 test('tcfail201', normal, compile_fail, [''])
 test('tcfail202', normal, compile_fail, [''])
-# -Werror is a temporary hack. Once GHC makes this an error, rather
-# than a warning, we won't need it.
-test('tcfail203', normal, compile_fail, ['-Werror'])
+test('tcfail203', expect_broken(2806), compile_fail, [''])
 
 test('T1899', normal, compile_fail, [''])
 test('T2126', normal, compile_fail, [''])

testsuite/tests/ghc-regress/typecheck/should_fail/tcfail203.hs

@@ -48,3 +48,6 @@ fail8 = 'a'
 fail9 = 'a'
     where (# b, !x #) = (# True, 5# #)
 
+fail10 = 'a'
+    where !(b, ~(c, (I# x))) = (True, (False, 5))
+

testsuite/tests/ghc-regress/typecheck/should_fail/tcfail203.stderr

@@ -71,6 +71,9 @@ tcfail203.hs:49:10:
               where
                   (# b, !x #) = (# True, 5# #)
 
-<no location info>: 
-Failing due to -Werror.
+tcfail203.hs:52:15:
+    A lazy (~) pattern cannot contain unlifted types ~(c, (I# x))
+    In the pattern: ~(c, (I# x))
+    In the pattern: (b, ~(c, (I# x)))
+    In the pattern: !(b, ~(c, (I# x)))