Improve test

testsuite/tests/typecheck/should_fail/T7609.hs

@@ -6,3 +6,6 @@ data X a b
 
 f :: (a `X` a, Maybe)
 f = undefined
+
+g :: (a `X` a) => Maybe
+g = undefined
\ No newline at end of file

testsuite/tests/typecheck/should_fail/T7609.stderr

@@ -4,3 +4,8 @@ T7609.hs:7:16:
     The second argument of a tuple should have kind `*',
       but `Maybe' has kind `* -> *'
     In the type signature for `f': f :: (a `X` a, Maybe)
+
+T7609.hs:10:19:
+    Expecting one more argument to `Maybe'
+    Expected a type, but `Maybe' has kind `* -> *'
+    In the type signature for `g': g :: a `X` a => Maybe