src/jdk.vm.ci/share/classes/jdk.vm.ci.meta/src/jdk/vm/ci/meta/Assumptions.java

@@ -42,11 +42,14 @@
     public abstract static class Assumption {
     }
 
     /**
      * A class for providing information that is only valid in association with a set of
-     * {@link Assumption}s.
+     * {@link Assumption}s. It is permissible for AssumptionResults to have no assumptions at all.
+     * For instance, if {@link ResolvedJavaType#isLeaf()} returns true for a type
+     * {@link ResolvedJavaType#findLeafConcreteSubtype()} can return an AssumptionResult with no
+     * assumptions since the leaf information is statically true.
      *
      * @param <T>
      */
     public static class AssumptionResult<T> {
         Assumption[] assumptions;

@@ -185,10 +188,11 @@
          * Type the assumption is made about.
          */
         public final ResolvedJavaType context;
 
         public LeafType(ResolvedJavaType context) {
+            assert !context.isLeaf() : "assumption isn't required for leaf types";
             this.context = context;
         }
 
         @Override
         public int hashCode() {