diff --git a/lang/funcs/operator_func.go b/lang/funcs/operator_func.go
index 00db6a23..018c54c6 100644
--- a/lang/funcs/operator_func.go
+++ b/lang/funcs/operator_func.go
@@ -883,10 +883,27 @@ func (obj *OperatorFunc) Stream(ctx context.Context) error {
 			}
 			obj.last = input // store for next
 
+			// programming error safety check...
+			programmingError := false
+			keys := []string{}
+			for k := range input.Struct() {
+				keys = append(keys, k)
+				if !util.StrInList(k, obj.Type.Ord) {
+					programmingError = true
+				}
+			}
+			if programmingError {
+				return fmt.Errorf("bad args, got: %v, want: %v", keys, obj.Type.Ord)
+			}
+
 			// build up arg list
 			args := []types.Value{}
 			for _, name := range obj.Type.Ord {
-				v := input.Struct()[name]
+				v, exists := input.Struct()[name]
+				if !exists {
+					// programming error
+					return fmt.Errorf("function engine was early, missing arg: %s", name)
+				}
 				if name == operatorArgName {
 					op = v.Str()
 					continue // skip over the operator arg
@@ -895,7 +912,8 @@ func (obj *OperatorFunc) Stream(ctx context.Context) error {
 			}
 
 			if op == "" {
-				return fmt.Errorf("operator cannot be empty")
+				// programming error
+				return fmt.Errorf("operator cannot be empty, args: %v", keys)
 			}
 			// operator selection is dynamic now, although mostly it
 			// should not change... to do so is probably uncommon...
diff --git a/lang/funcs/simple/simple.go b/lang/funcs/simple/simple.go
index f9d4be05..28e83e71 100644
--- a/lang/funcs/simple/simple.go
+++ b/lang/funcs/simple/simple.go
@@ -84,7 +84,7 @@ type WrappedFunc struct {
 // String returns a simple name for this function. This is needed so this struct
 // can satisfy the pgraph.Vertex interface.
 func (obj *WrappedFunc) String() string {
-	return fmt.Sprintf("%s@%p", obj.Name, obj) // be more unique!
+	return fmt.Sprintf("%s @ %p", obj.Name, obj) // be more unique!
 }
 
 // ArgGen returns the Nth arg name for this function.
diff --git a/lang/funcs/simplepoly/simplepoly.go b/lang/funcs/simplepoly/simplepoly.go
index 26102cd1..d9f22a59 100644
--- a/lang/funcs/simplepoly/simplepoly.go
+++ b/lang/funcs/simplepoly/simplepoly.go
@@ -149,7 +149,7 @@ type WrappedFunc struct {
 // String returns a simple name for this function. This is needed so this struct
 // can satisfy the pgraph.Vertex interface.
 func (obj *WrappedFunc) String() string {
-	return fmt.Sprintf("%s@%p", obj.Name, obj) // be more unique!
+	return fmt.Sprintf("%s @ %p", obj.Name, obj) // be more unique!
 }
 
 // ArgGen returns the Nth arg name for this function.
@@ -501,9 +501,8 @@ func (obj *WrappedFunc) buildFunction(typ *types.Type, ix int) *types.Type {
 		panic("unexpected type")
 	}
 	obj.fn = fn
-	if obj.fn.T == nil { // XXX: should this even ever happen? What about argnames here?
-		obj.fn.T = typ.Copy() // overwrites any contained "variant" type
-	}
+	// FIXME: if obj.fn.T == nil {} // occasionally this is nil, is it a bug?
+	obj.fn.T = typ.Copy() // overwrites any contained "variant" type
 
 	return obj.fn.T
 }