Add a couple of tests for #3811

testsuite/tests/ghc-regress/parser/should_fail/T3811.hs

+
+module T3811 where
+
+f x :: Char
+f x = 'c'

testsuite/tests/ghc-regress/parser/should_fail/T3811.stderr

+
+T3811.hs:4:1:
+    Invalid type signature: f x :: Char
+    Should be of form <variable> :: <type>

testsuite/tests/ghc-regress/parser/should_fail/T3811b.hs

+
+module T3811b where
+
+data Foo a = !B

testsuite/tests/ghc-regress/parser/should_fail/T3811b.stderr

+
+T3811b.hs:4:14:
+    parse error in constructor in data/newtype declaration: !B

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

@@ -63,3 +63,5 @@ test('position002', normal, compile_fail, [''])
 test('T1344a', normal, compile_fail, [''])
 test('T1344b', normal, compile_fail, [''])
 test('T1344c', normal, compile_fail, [''])
+test('T3811', normal, compile_fail, [''])
+test('T3811b', normal, compile_fail, [''])