diff --git a/tlatools/org.lamport.tlatools/src/org/eclipse/xtext/xbase/lib/Pure.java b/tlatools/org.lamport.tlatools/src/org/eclipse/xtext/xbase/lib/Pure.java
new file mode 100644
index 0000000000..48d75fddc0
--- /dev/null
+++ b/tlatools/org.lamport.tlatools/src/org/eclipse/xtext/xbase/lib/Pure.java
@@ -0,0 +1,16 @@
+package org.eclipse.xtext.xbase.lib;
+
+import static java.lang.annotation.ElementType.CONSTRUCTOR;
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+@Documented
+@Retention(RUNTIME)
+@Target({ METHOD, CONSTRUCTOR })
+public @interface Pure {
+
+}
diff --git a/tlatools/org.lamport.tlatools/src/org/eclipse/xtext/xbase/lib/util/ToStringBuilder.java b/tlatools/org.lamport.tlatools/src/org/eclipse/xtext/xbase/lib/util/ToStringBuilder.java
new file mode 100644
index 0000000000..07153f21f0
--- /dev/null
+++ b/tlatools/org.lamport.tlatools/src/org/eclipse/xtext/xbase/lib/util/ToStringBuilder.java
@@ -0,0 +1,15 @@
+package org.eclipse.xtext.xbase.lib.util;
+
+public class ToStringBuilder {
+	
+	public ToStringBuilder(Object instance) {
+	}
+	
+	public ToStringBuilder add(Object value) {
+		return this;
+	}
+
+	public ToStringBuilder add(String fieldName, Object value) {
+		return this;
+	}
+}