+-- qualified operator NOTES.
+--
+-- - If M.(+) is a single lexeme, then..
+-- - Probably (+) should be a single lexeme too, for consistency.
+-- Otherwise ( + ) would be a prefix operator, but M.( + ) would not be.
+-- - But we have to rule out reserved operators, otherwise (..) becomes
+-- a different lexeme.
+-- - Should we therefore also rule out reserved operators in the qualified
+-- form? This is quite difficult to achieve. We don't do it for
+-- qualified varids.
+