Update dependencies (#5518)

vendor/github.com/open-policy-agent/opa/ast/transform.go

@@ -13,7 +13,7 @@ import (
 // be set to nil and no transformations will be applied to children of the
 // element.
 type Transformer interface {
-	Transform(v interface{}) (interface{}, error)
+	Transform(interface{}) (interface{}, error)
 }
 
 // Transform iterates the AST and calls the Transform function on the
@@ -116,6 +116,9 @@ func Transform(t Transformer, x interface{}) (interface{}, error) {
 		}
 		return y, nil
 	case *Head:
+		if y.Reference, err = transformRef(t, y.Reference); err != nil {
+			return nil, err
+		}
 		if y.Name, err = transformVar(t, y.Name); err != nil {
 			return nil, err
 		}
@@ -327,7 +330,7 @@ func TransformComprehensions(x interface{}, f func(interface{}) (Value, error))
 // GenericTransformer implements the Transformer interface to provide a utility
 // to transform AST nodes using a closure.
 type GenericTransformer struct {
-	f func(x interface{}) (interface{}, error)
+	f func(interface{}) (interface{}, error)
 }
 
 // NewGenericTransformer returns a new GenericTransformer that will transform
@@ -414,3 +417,15 @@ func transformVar(t Transformer, v Var) (Var, error) {
 	}
 	return r, nil
 }
+
+func transformRef(t Transformer, r Ref) (Ref, error) {
+	r1, err := Transform(t, r)
+	if err != nil {
+		return nil, err
+	}
+	r2, ok := r1.(Ref)
+	if !ok {
+		return nil, fmt.Errorf("illegal transform: %T != %T", r, r2)
+	}
+	return r2, nil
+}