2 files changed, 10 insertions, 2 deletions
diff --git a/chapter17/src/main/java/com/seaofnodes/simple/node/StopNode.java b/chapter17/src/main/java/com/seaofnodes/simple/node/StopNode.java
index fb8c3cc4..e498141e 100644
--- a/chapter17/src/main/java/com/seaofnodes/simple/node/StopNode.java
+++ b/chapter17/src/main/java/com/seaofnodes/simple/node/StopNode.java
@@ -68,9 +68,15 @@ public class StopNode extends CFGNode {
     }
 
     public StopNode iterate() { return IterPeeps.iterate(this).typeCheck().GCM(); }
-    StopNode typeCheck() {
-        String err = walk( Node::err );
+    public StopNode typeCheck() {
+        var obs = Parser.PARSER == null ? null : Parser.PARSER._obs;
+        String err = walk(n -> {
+            String msg = n.err();
+            if( msg != null && obs != null ) obs.error(n, msg);
+            return msg;
+        });
         if( err != null ) throw new RuntimeException(err);
+        if( obs != null ) obs.phase("TypeCheck");
         return this;
     }
     StopNode GCM() {
diff --git a/chapter17/src/main/java/com/seaofnodes/simple/print/SimpleGraphObserver.java b/chapter17/src/main/java/com/seaofnodes/simple/print/SimpleGraphObserver.java
index 38f84d7d..d774967b 100644
--- a/chapter17/src/main/java/com/seaofnodes/simple/print/SimpleGraphObserver.java
+++ b/chapter17/src/main/java/com/seaofnodes/simple/print/SimpleGraphObserver.java
@@ -25,6 +25,8 @@ public class SimpleGraphObserver extends GraphCapture<Node> {
         _phase = "Iter";
         com.seaofnodes.simple.IterPeeps.iterate(_parser.STOP);
         phase(_phase);
+        _phase = "TypeCheck";
+        _parser.STOP.typeCheck();
     }
     @Override protected String phase() { return _phase; }
     @Override protected int pos() { return "Parse".equals(_phase) ? _parser.pos() : -1; }