* New builtin function "isFunction". You're not supposed to use it

;-)
* Channels: fix channels that are plain lists of derivations (like
  strategoxt-unstable) instead  of functions (like nixpkgs-unstable).
  This fixes the error message "error: the left-hand side of the
  function call is neither a function nor a primop (built-in
  operation) but a list".

src/libexpr/eval.cc

@@ -478,7 +478,7 @@ LocalNoInline(Expr evalCall(EvalState & state, Expr fun, Expr arg))
     }
 
     else throwTypeError(
-        "the left-hand side of the function call is neither a function nor a primop (built-in operation) but %1%",
+        "attempt to call something which is neither a function nor a primop (built-in operation) but %1%",
         showType(fun));
 }