diff --git a/src/main/java/suite/funp/Funp_.java b/src/main/java/suite/funp/Funp_.java
index 8e5bd845f..1b20b83cc 100644
--- a/src/main/java/suite/funp/Funp_.java
+++ b/src/main/java/suite/funp/Funp_.java
@@ -42,6 +42,7 @@
 import suite.node.parser.IterativeParser;
 import suite.node.util.Singleton;
 import suite.object.CastDefaults;
+import suite.object.MetadataDefaults;
 import suite.object.SwitchDefaults;
 import suite.util.Switch;
 
@@ -54,7 +55,10 @@ public class Funp_ extends FunpCfg {
 
 	public boolean isOptimize;
 
-	public interface Funp extends CastDefaults<Funp>, SwitchDefaults<Funp> {
+	public interface Funp extends CastDefaults<Funp>, MetadataDefaults<FunpMetadata>, SwitchDefaults<Funp> {
+	}
+
+	public static class FunpMetadata {
 	}
 
 	public static class CompileException extends RuntimeException {
diff --git a/src/main/java/suite/funp/SwitchFunp.java b/src/main/java/suite/funp/SwitchFunp.java
new file mode 100644
index 000000000..ce19e63f7
--- /dev/null
+++ b/src/main/java/suite/funp/SwitchFunp.java
@@ -0,0 +1,23 @@
+package suite.funp;
+
+import suite.funp.Funp_.Funp;
+import suite.funp.Funp_.FunpMetadata;
+import suite.util.Switch;
+
+public class SwitchFunp extends Switch<Funp> {
+
+	private FunpMetadata metadata;
+
+	public SwitchFunp(Funp in) {
+		super(in);
+		metadata = in.getMetadata();
+	}
+
+	public Funp result() {
+		var result = super.result();
+		if (result != null)
+			result.setMetadata(metadata);
+		return result;
+	}
+
+}
diff --git a/src/main/java/suite/node/Node.java b/src/main/java/suite/node/Node.java
index 0eeb13f7b..a19863c9d 100644
--- a/src/main/java/suite/node/Node.java
+++ b/src/main/java/suite/node/Node.java
@@ -2,8 +2,9 @@
 
 import suite.node.io.Formatter;
 import suite.node.util.Comparer;
+import suite.object.MetadataDefaults;
 
-public abstract class Node implements Comparable<Node> {
+public abstract class Node implements Comparable<Node>, MetadataDefaults<Node> {
 
 	public Node finalNode() {
 		return this;
diff --git a/src/main/java/suite/node/io/SwitchNode.java b/src/main/java/suite/node/io/SwitchNode.java
index 34a91a390..ffbf4cd5c 100644
--- a/src/main/java/suite/node/io/SwitchNode.java
+++ b/src/main/java/suite/node/io/SwitchNode.java
@@ -147,6 +147,7 @@ public SwitchNode<R> matchArray(String pattern, Fun<Node[], R> fun) {
 	}
 
 	public R nonNullResult() {
+		var result = result();
 		return result != null ? result : fail("cannot handle " + in);
 	}
 
diff --git a/src/main/java/suite/object/MetadataDefaults.java b/src/main/java/suite/object/MetadataDefaults.java
new file mode 100644
index 000000000..8038e3608
--- /dev/null
+++ b/src/main/java/suite/object/MetadataDefaults.java
@@ -0,0 +1,22 @@
+package suite.object;
+
+import java.util.Map;
+import java.util.WeakHashMap;
+
+public interface MetadataDefaults<T> {
+
+	public static Map<Object, Object> metadata = new WeakHashMap<>();
+
+	public default T getMetadata() {
+		@SuppressWarnings("unchecked")
+		var t = (T) metadata.get(this);
+		return t;
+	}
+
+	public default T setMetadata(T t) {
+		@SuppressWarnings("unchecked")
+		T t0 = (T) metadata.put(this, t);
+		return t0;
+	}
+
+}
diff --git a/src/main/java/suite/util/Switch.java b/src/main/java/suite/util/Switch.java
index 50b9dd9b6..2d7b4b876 100644
--- a/src/main/java/suite/util/Switch.java
+++ b/src/main/java/suite/util/Switch.java
@@ -33,6 +33,7 @@ public <T> Switch<R> doIf(Class<T> c, IoSink<T> fun) {
 	}
 
 	public R nonNullResult() {
+		var result = result();
 		return result != null ? result : fail("cannot handle " + in);
 	}