Error change following up kind constraint solving modificatios.

testsuite/tests/indexed-types/should_fail/T3330c.stderr

-
-T3330c.hs:23:43:
-    Couldn't match type `Der ((->) x)' with `R'
-    In the first argument of `plug', namely `rf'
-    In the first argument of `Inl', namely `(plug rf df x)'
-    In the expression: Inl (plug rf df x)
-
-T3330c.hs:23:43:
-    Couldn't match type `f1' with `f1 x'
-      `f1' is a rigid type variable bound by
-           a pattern with constructor
-             RSum :: forall (f :: * -> *) (g :: * -> *).
-                     R f -> R g -> R (f :+: g),
-           in an equation for plug'
-           at T3330c.hs:23:8
-    In the first argument of `plug', namely `rf'
-    In the first argument of `Inl', namely `(plug rf df x)'
-    In the expression: Inl (plug rf df x)
+
+T3330c.hs:23:33:
+    Kind incompatibility when matching types:
+      f0 :: * -> *
+      f0 x :: *
+    In the return type of a call of `Inl'
+    In the expression: Inl (plug rf df x)
+    In an equation for plug':
+        plug' (RSum rf rg) (Inl df) x = Inl (plug rf df x)
+
+T3330c.hs:23:43:
+    Couldn't match kind `*' with `* -> *'
+    Kind incompatibility when matching types:
+      Der ((->) x) :: * -> *
+      R :: (* -> *) -> *
+    In the first argument of `plug', namely `rf'
+    In the first argument of `Inl', namely `(plug rf df x)'