--- a/ParseNodeVisitor.st	Tue Sep 03 16:16:22 2019 +0200
+++ b/ParseNodeVisitor.st	Fri Sep 06 09:54:50 2019 +0200
@@ -1,9 +1,11 @@
+"{ Encoding: utf8 }"
+
 "{ Package: 'stx:libcomp' }"
 
 "{ NameSpace: Smalltalk }"
 
 Object subclass:#ParseNodeVisitor
-	instanceVariableNames:''
+	instanceVariableNames:'pluggableActionsPerNodeType'
 	classVariableNames:''
 	poolDictionaries:''
 	category:'System-Compiler-Support'
@@ -18,10 +20,29 @@
 "    
 ! !
 
+!ParseNodeVisitor methodsFor:'pluggable setup'!
+
+actionForNodeClass:aNodeClass put:aBlock
+    "setup so that for nodes of type aNodeClass, aBlock is invoked.
+     If the block returns true, subnodes (eg. right side of assignments, etc.)
+     will be enumerated as well.
+     Otherwise, no subnodes are visited."
+
+    pluggableActionsPerNodeType isNil ifTrue:[
+         pluggableActionsPerNodeType := Dictionary new.
+    ].
+    pluggableActionsPerNodeType at:aNodeClass put:aBlock
+! !
+
 !ParseNodeVisitor methodsFor:'visiting'!
 
 visit:anObject 
-    | stmt lastResult |
+    |action stmt lastResult|
+
+    action := pluggableActionsPerNodeType at:(anObject class) ifAbsent:[nil].
+    action notNil ifTrue:[ 
+        (action value:anObject) ifFalse:[^ self].
+    ].
 
     anObject isStatementNode ifTrue:[
         stmt := anObject.