[project @ 2005-05-04 10:31:12 by ross]

add output -- not the best error message, but it's hard to see how
we can do better.

testsuite/tests/ghc-regress/arrows/arrow1.stderr

+
+arrow1.hs:15:35:
+    Ambiguous type variable `a' in the constraint:
+      `Foo a' arising from use of `foo' at arrow1.hs:15:35-37
+    Probable fix: add a type signature that fixes these type variable(s)